Weekly ACAS Review · Continental US

Military–Civilian TCAS Resolution Advisories

Week of 2026-06-04 — 2026-06-10 (UTC) · Generated 2026-06-10 from archived ACAS & ADS-B data

The prompt that produced this report “Look at the past week of TCAS RAs. Find significant incidents with military aircraft vs civilian aircraft. Calculate the closest point of approach, tau, and whether each aircraft in the incident that got an RA complied with it, and how quickly they complied. Create an HTML report.”

Of roughly 6,400 RA messages involving military aircraft recorded this week, the overwhelming majority were military-on-military trainer encounters (T-38 formation and MOA work around UPT bases). Five encounters stood out as significant military-vs-civilian conflicts — airline or civil aircraft and a military aircraft, with an active (corrective or preventive) resolution advisory. Every aircraft that received an RA responded correctly; in three of the five encounters the military aircraft carried no TCAS II, so resolution depended entirely on the civilian crew.

Significant military–civilian conflicts

100%

RA compliance — every advisory flown correctly

3 / 5

Encounters where the military aircraft had no TCAS II

	Date / CPA (UTC)	Location	Civil	Military	CPA lateral (nm)	CPA vert (ft)	min τ (s)	RAs
E1	2026-06-10 00:27:47Z	Near Roxboro, NC	SWA699	ae6827	2.11	1500	31	2/2
E2	2026-06-10 15:53:15Z	Miami Lakes, FL	EJA984	C2317	0.32	475	15	2/2
E3	2026-06-05 16:00:08Z	Mouth of the Potomac River, MD	SWA1044	(T-38)	0.31	1484	28	1/2
E4	2026-06-06 01:29:36Z	Near Jean, NV	ASA779	DESERT8	1.97	925	33	1/2
E5	2026-06-07 16:55:50Z	Perris, CA	PERRIS1	SLAM78	0.71	503	13	1/2

E1. Head-on at FL320: Southwest 737 vs unidentified military aircraft

2026-06-10 · CPA at 2026-06-10 00:27:47Z · Near Roxboro, NC (35 nm N of Raleigh-Durham)

SWA699 (N206WN, Boeing 737-700) was descending out of FL350 while an unidentified US military aircraft (hex ae6827, broadcasting no callsign, registration, or type) cruised at ~FL320 on a nearly reciprocal heading — closure rate roughly 800 kt. As SWA699 leveled at FL323, only ~325 ft above the military aircraft and 7–8 nm ahead, both aircraft received coordinated, complementary RAs: the military aircraft was first commanded DESCEND, and ~4.7 s later SWA699 received CLIMB ("do not pass below"). Both aircraft maneuvered correctly and built ~1,500 ft of vertical separation by the time they crossed 2.1 nm abeam. The coordination (one up, one down) confirms the military aircraft was TCAS II–equipped and responding — likely a transport/tanker-class airframe. The anonymous Mode-S setup (military hex, no identity broadcast) is notable at civil cruise altitudes.

Who is ae6827? The hex first appeared on 2026-06-09 — the day before this encounter — and belongs to a block of anonymized US military addresses (neighbors broadcast callsigns like SAM596 and BLKCAT5, or nothing at all). Its three days of flight history all originate and terminate at NAS Jacksonville: a Jun 9 night sortie to Harrisburg, PA (~95 min of low approaches at KMDT, home of the 193rd Special Operations Wing) — this RA occurred on the return leg — and a Jun 10 sortie to Little Rock AFB (~65 min of approaches at the USAF's C-130J schoolhouse). Its performance envelope is distinctive: ~400 KTAS block speed at FL310–330 with maximum observed speed of exactly Mach 0.68 — the C-130J's Mmo — far below a P-8 or C-40 (Mmo 0.82) and above a legacy C-130H. Best assessment: a brand-new C-130J, most likely a US Navy Reserve KC-130J of VR-62 (which is currently replacing its C-130Ts at NAS Jacksonville), flying crew work-up sorties. Confidence: high on the C-130J family, moderate on the VR-62/KC-130J attribution.

Aircraft	Type / operator	Mode-S	TCAS
SWA699	Southwest 737-700 N206WN	`a1aa4e`	TCAS II, RA received
ae6827	Unidentified US military — assessed as new-production C-130J, likely a US Navy Reserve KC-130J (VR-62, NAS Jacksonville); see narrative	`ae6827`	TCAS II, RA received

Closest point of approach	Lateral	Vertical	Altitudes	Position
2026-06-10 00:27:47Z	2.11 nm (3899 m)	1500 ft	33,150 / 31,650 ft	36.4501, -78.9009

Aircraft	RA sequence (UTC)	Range at RA (slant / vert)	τ at RA	Closure	VS at RA (fpm)	RA duration	Compliance
SWA699	Climb (do not pass below) 00:27:19 → Level Off 00:27:29 → CoC 00:27:34	6.79 nm / 375 ft	30.6 s	799 kt	+784	14.8 s	COMPLIED Initiated climb ≈4–5 s after RA; altitude from the 1 Hz RA messages shows +300 ft in 6.1 s (≈+2,900 fpm) — well past the +1,500 fpm target ≈5–6 s after issue. RA weakened to Level Off after 9.9 s as the conflict resolved, then Clear of Conflict at 14.8 s.
ae6827	Descend 00:27:15 → Descend (do not pass above) 00:27:20 → Level Off 00:27:26 → CoC 00:27:31	7.85 nm / 320 ft	34.9 s	810 kt	-483	16.4 s	COMPLIED Initiated descent ≈4–5 s after RA; RA-message altitudes show −200 ft over 5.7 s (≈−2,100 fpm), crossing the −1,500 fpm target ≈6–7 s after issue. RA weakened to Level Off at 11.5 s, Clear of Conflict at 16.4 s.

Track positions for this encounter come from the 48-h live feed (~17 s snapshots); CPA is interpolated. Compliance timing uses the 1 Hz altitudes embedded in the RA messages themselves.

Charts span 2 min before the first RA to 2 min after Clear of Conflict. Top: barometric altitude, both aircraft, with RA / Clear-of-Conflict / CPA markers. Middle: lateral separation. Bottom: vertical separation.

globe.airplanes.live: both aircraft at the moment of closest approach near Roxboro, NC — SWA699 descending out of FL350 meets the unidentified military aircraft at ~FL320 nearly head-on. Track labels show ground speed, altitude, and UTC time. Click to open the interactive view.

Replay: globe.airplanes.live — both tracks, 00:25:15–00:29:34Z
3-D geometry: cpa.skycircl.es

E2. NetJets vs Coast Guard HC-144 at 1,500 ft over Miami

2026-06-10 · CPA at 2026-06-10 15:53:15Z · Miami Lakes, FL — 5 nm from Opa-locka Executive (KOPF)

EJA984 (N984QS, NetJets) was level at 1,850 ft in the Opa-locka terminal area when it crossed paths with US Coast Guard HC-144B Ocean Sentry #2317 (Air Station Miami is based at Opa-locka), level at 1,375 ft. Both aircraft received simultaneous preventive "Monitor vertical speed" RAs — TCAS judged the existing 475 ft of vertical separation adequate as long as neither aircraft maneuvered into the other. They crossed just 0.33 nm apart laterally with 475 ft vertical — the tightest lateral CPA of the week's military-civil encounters. Tau at RA issue was only ~15 s (RAs fire later at low altitude by design).

Aircraft	Type / operator	Mode-S	TCAS
EJA984	NetJets Bombardier N984QS	`adbb6f`	TCAS II, RA received
C2317	USCG HC-144B Ocean Sentry 2317	`ae4bf1`	TCAS II, RA received

Closest point of approach	Lateral	Vertical	Altitudes	Position
2026-06-10 15:53:15Z	0.32 nm (596 m)	475 ft	1,850 / 1,375 ft	25.9293, -80.3929

Aircraft	RA sequence (UTC)	Range at RA (slant / vert)	τ at RA	Closure	VS at RA (fpm)	RA duration	Compliance
EJA984	Monitor vertical Speed (do not pass below) 15:53:01 → CoC 15:53:20	1.06 nm / 482 ft	15.5 s	246 kt	+136	18.5 s	COMPLIED (preventive) Preventive RA — requirement is to hold vertical speed, which the crew did until Clear of Conflict.
C2317	Monitor vertical Speed 15:53:01 → CoC 15:53:21	1.06 nm / 482 ft	15.5 s	246 kt	-9	19.5 s	COMPLIED (preventive) Preventive RA — requirement is to hold vertical speed, which the crew did until Clear of Conflict.

Track positions from the 48-h live feed (~17 s snapshots); CPA interpolated. Both RAs were preventive — compliance means holding vertical speed, which both did.

globe.airplanes.live: EJA984 and Coast Guard 2317 at the moment of closest approach over Miami Lakes, converging tracks at 1,375–1,850 ft in the Opa-locka terminal area. Click to open the interactive view.

Replay: globe.airplanes.live — both tracks, 15:51:01–15:55:21Z
3-D geometry: cpa.skycircl.es

E3. 900-kt closure: Southwest 737 vs T-38 Talon near Patuxent River

2026-06-05 · CPA at 2026-06-05 16:00:08Z · Mouth of the Potomac River, MD (near NAS Patuxent River)

SWA1044 (N479WN, 737-700) was climbing through FL254 at +2,050 fpm when a USAF T-38A Talon (67-14923) crossed ahead, 1,700 ft above, at a combined closure of ≈900 kt. TCAS issued a Level Off RA 28 s before closest approach; the crew complied within ~10 s, stopping the climb at FL256. The T-38 passed just 0.31 nm laterally — about 575 m — with ~1,500 ft of vertical separation that existed only because the 737 stopped climbing. The T-38 broadcast no RA (T-38s are not TCAS II–equipped), so the entire resolution depended on the Southwest crew.

Aircraft	Type / operator	Mode-S	TCAS
SWA1044	Southwest 737-700 N479WN	`a5e48a`	TCAS II, RA received
(T-38)	USAF T-38A Talon 67-14923	`ae63fa`	No RA broadcast (likely no TCAS II)

Closest point of approach	Lateral	Vertical	Altitudes	Position
2026-06-05 16:00:08Z	0.31 nm (566 m)	1484 ft	25,625 / 27,109 ft	38.1544, -76.6724

Aircraft	RA sequence (UTC)	Range at RA (slant / vert)	τ at RA	Closure	VS at RA (fpm)	RA duration	Compliance
SWA1044	Level Off 15:59:40 → CoC 16:00:14	7.05 nm / 1687 ft	28.2 s	899 kt	+2,048	33.6 s	COMPLIED met the RA target (\|VS\| <= 250 fpm) 10.0 s after issue.

globe.airplanes.live: SWA1044 climbing northbound across the mouth of the Potomac as the T-38 converges at ~900 kt combined closure; aircraft shown at the moment of closest approach. Click to open the interactive view.

Replay: globe.airplanes.live — both tracks, 15:57:40–16:02:14Z
3-D geometry: cpa.skycircl.es

E4. Alaska 737 MAX climbing out of Las Vegas vs C-27J Spartan

2026-06-06 · CPA at 2026-06-06 01:29:36Z · Near Jean, NV — 15 nm SW of Las Vegas (KLAS departure corridor)

ASA779 (N729AL, 737 MAX 9) departed Las Vegas and was climbing at +2,700 fpm through 10,300 ft when USAF C-27J Spartan 10-27028 (DESERT8) crossed 1,100 ft above and 3.2 nm ahead. TCAS issued Level Off; the crew complied within ~9.5 s, capping the climb at 10,575 ft. CPA was 1.97 nm / ~925 ft. The C-27J reported no RA of its own. A routine but clean example of an RA protecting a busy departure corridor from a military crosser.

Aircraft	Type / operator	Mode-S	TCAS
ASA779	Alaska 737 MAX 9 N729AL	`a9c506`	TCAS II, RA received
DESERT8	USAF C-27J Spartan 10-27028	`ae4cfc`	No RA broadcast (likely no TCAS II)

Closest point of approach	Lateral	Vertical	Altitudes	Position
2026-06-06 01:29:36Z	1.97 nm (3651 m)	925 ft	10,525 / 11,450 ft	35.8880, -115.3798

Aircraft	RA sequence (UTC)	Range at RA (slant / vert)	τ at RA	Closure	VS at RA (fpm)	RA duration	Compliance
ASA779	Level Off 01:29:12 → CoC 01:29:27	3.21 nm / 1139 ft	33.1 s	350 kt	+2,688	14.6 s	COMPLIED met the RA target (\|VS\| <= 250 fpm) 9.5 s after issue.

globe.airplanes.live: ASA779 climbing out of Las Vegas with DESERT8 crossing ahead near Jean, NV; aircraft shown at the moment of closest approach. Click to open the interactive view.

Replay: globe.airplanes.live — both tracks, 01:27:12–01:31:27Z
3-D geometry: cpa.skycircl.es

E5. C-17 vs skydiving Twin Otter over the Perris drop zone

2026-06-07 · CPA at 2026-06-07 16:55:50Z · Perris, CA — 2 nm from Perris Valley Airport (skydiving DZ)

C-17A Globemaster 94-0068 (SLAM78) was at 4,075 ft near Perris — 4 km from Perris Valley Airport, one of the busiest skydiving drop zones in the country — when its TCAS issued a DESCEND RA against PERRIS1 (N125SA), a DHC-6 Twin Otter jump plane in a steep post-jump-run descent: it had left ~14,300 ft (jump altitude) four minutes earlier and was diving at ≈−3,000 fpm, passing ~4,800 ft — 926 ft above the C-17 and coming down onto it — when the RA fired. Tau at RA issue was just 13 s at 1.2 nm range. The C-17 crew responded fast: descent initiated in ~5.5 s, exceeding the −1,500 fpm target in 7.5 s and peaking at ≈−2,800 fpm — an escape below the descending jump plane — before Clear of Conflict 13.8 s after the RA. CPA was 0.71 nm / ~500 ft with the Twin Otter still above. The Twin Otter (no TCAS II) never altered its dive.

Aircraft	Type / operator	Mode-S	TCAS
PERRIS1	DHC-6 Twin Otter N125SA (skydive)	`a067d6`	No RA broadcast (likely no TCAS II)
SLAM78	USAF C-17A 94-0068	`ae07e2`	TCAS II, RA received

Closest point of approach	Lateral	Vertical	Altitudes	Position
2026-06-07 16:55:50Z	0.71 nm (1313 m)	503 ft	4,440 / 3,937 ft	33.7933, -117.2602

Aircraft	RA sequence (UTC)	Range at RA (slant / vert)	τ at RA	Closure	VS at RA (fpm)	RA duration	Compliance
SLAM78	Descend 16:55:40 → CoC 16:55:54	1.20 nm / 926 ft	13.4 s	322 kt	+0	13.8 s	COMPLIED response initiated ≈5.5 s after RA; met the RA target (VS <= -1500 fpm) 7.5 s after issue; peak vertical rate -2,778 fpm.

3-D reconstruction of the encounter at CPA (cpa.skycircl.es): PERRIS1's S-turning descent from jump altitude (red) comes down onto SLAM78, lower right with its RA position reports marked; the connector shows the 0.71 nm / 506 ft closest approach. Click to open the interactive view.

Replay: globe.airplanes.live — both tracks, 16:53:40–16:57:54Z
3-D geometry: cpa.skycircl.es

Method & caveats

Sources. ADS-B tracks and ACAS Resolution Advisory events from airplanes.live and adsb.lol. RA events: historical ACAS archive + a near-realtime ACAS feed. Tracks: daily ADS-B trace archive (≈1 Hz) for Jun 5–7 events; 48-h live snapshot feed (≈17 s) for Jun 10 events.
CPA computed by linearly interpolating both aircraft's positions/altitudes onto a common 0.5 s grid and taking the minimum slant range. For the 17 s-sampled encounters (E1, E2) the true CPA may differ by a few hundred meters.
Tau (τ) = slant range ÷ closure rate at the moment the first RA message was received, range rate from an ±4 s centered difference. This approximates the TCAS range-tau that drives RA timing.
Compliance: corrective Climb/Descend RAs require ±1,500 fpm (Increase: 2,500 fpm); Level Off requires arresting vertical rate to ≈0; "Monitor vertical speed" is preventive (hold current VS). Vertical rates from broadcast baro rate, cross-checked against the 1 Hz altitudes carried in the RA messages themselves. "Time to comply" is time from first RA message to first meeting the target rate.
Limits. RA detection depends on ground-receiver coverage — aircraft without coverage or without TCAS II (T-38, DHC-6) show no RA even when they were the conflict traffic. Altitudes are 25 ft-quantized barometric. The unidentified aircraft in E1 is classified military by its ICAO hex allocation (ae6827, US military block).