A Transavia France Boeing 737-800 flying from Madrid to Paris Orly squawked 7700 on Saturday 7 November after a descent from 28,000 feet over northern Spain, then diverted to Bordeaux Mérignac123. The aircraft was F-GZHM, operating flight TO4635 under the callsign TVF25BV145. No reason for the emergency has been reported so far.

What the ADS-B data shows

All times are UTC, from the adsb.lol trace of F-GZHM1. The aircraft got airborne from Madrid at about 14:12 and was at 28,000 feet by about 14:23. About two minutes later it started down, with the vertical rate peaking at around 5,000 feet per minute. By about 14:31 it was at 11,000 feet and by 14:33 at around 10,000 feet, where it stayed for some 15 minutes. The selected altitude in the data stepped from 13,000 feet to 11,000 and then to 10,000 between 14:25 and 14:321.

The 7700 code first appears in the received data at 14:35:03, roughly ten minutes after the descent began1. Other reports put it at 14:41 or 14:4234. The aircraft continued north at around 10,000 feet, passing inland of Bilbao and then San Sebastián and Biarritz over the Bay of Biscay. It stepped down to 9,000 feet at about 14:50 and began its final descent at about 14:55. It touched down at Bordeaux at about 15:07. The transponder was still sending 7700 on the ground at the last received position at 15:141.

Reading the profile, with care

A level-off near 10,000 feet is the classic target for a cabin pressure problem. SKYbrary guidance says crews should don oxygen masks at the first indication and, if pressurisation cannot be regained without delay, begin an emergency descent to 10,000 feet or the minimum safe altitude, whichever is higher67. The initiation of that descent is a memory item on most types6. An emergency should be declared with a MAYDAY, with ATC told that the aircraft is descending7.

None of that is confirmed for this flight. A descent of this shape can have other causes. No operator statement describes what the crew dealt with. SKYbrary lists setting 7700 among the actions in an emergency descent6, so the ten-minute gap before the code is an open question. Under SKYbrary guidance on emergency transponder codes, aircraft already receiving an air traffic service should retain the code in use, while the pilot may select 7700 whenever there is specific reason to believe that is the best course of action8.

Another open point is the choice of Bordeaux. Reports at the time noted Bilbao, San Sebastián and Biarritz nearby4. The aircraft passed all three before landing further north, which the data shows but does not explain1. No reason for that choice has been reported.

Other recent Transavia France disruptions

The same airframe, F-GZHM, diverted to Porto on 30 October on flight TO9813 from Marrakech to Brest after the cabin depressurised9. On 31 October a different aircraft, A320neo F-HXSO, returned to Orly on flight TO3004 to Agadir about 49 minutes after departure. The airline has given no public explanation10. Nothing published links the three events.

All of this comes while Transavia France and its Dutch sister are moving from the Boeing 737 to the Airbus A320neo family. Air France-KLM said on 5 November that both businesses are progressing with that transition11. Candidates preparing for assessment can use the Transavia selection practice to see what is tested.

Why the 7700 matters to controllers

Code 7700 is the general emergency code. It tells controllers that something is wrong without saying what. Once it is selected, air traffic control units in the area receive an immediate alert46. On a pressurisation event the time at altitude is the critical variable, because emergency oxygen supply is limited: SKYbrary notes that the supply will last little more than 15 minutes, perhaps less7. Whether that applied here is not known.

What is not yet known

The key missing facts are the nature of the emergency, whether oxygen masks deployed, how many people were on board and how passengers continued to Paris. If Transavia France or an investigating authority publishes details, this article will be updated.