On January 17, 2026, TAP Air Portugal flight TP1240, an Airbus A320neo operating from Lisbon (LIS) to Prague (PRG), descended well below the Minimum Safe Altitude (MSA) while on approach into the Czech capital.
The Czech Civil Aviation Authority (UZPLN) disclosed the incident publicly on February 12, classifying it as a serious incident and formally opening an investigation. The crew of the aircraft, registered CS-TVG, responded to instructions from air traffic control and recovered safely. All passengers and crew landed without injury.
Weather and pressure settings
The METAR valid at the time of the incident was:
LKPR 171000Z 11006KT 2500 0900NE R06/P2000N R30/P2000N BR BCFG SCT003 BKN005 OVC012 02/02 Q1023 TEMPO 3000 BR BKN007
This indicates that the general visibility was 2,500 metres, as low as 900 metres to the northeast. Mist and patches of fog reported. Scattered clouds at 300 feet.
According to ADS-B data, the crew used 1023 hPa as their altimeter setting when transitioning from flight level to altitude. This was in line with the valid METAR. All altitude values below are MSL (Mean Sea Level) adjusted to the local pressure setting (with ADS-B raw data value in brackets), unless stated otherwise. ADS-B altitude data (and the barometric altitude shown on Flightradar24) is reported as feet above mean sea level at standard pressure (1013.25 hPa). Knowing the local pressure (QNH) allows us to convert the altitude sent as part of the ADS-B data to the altitude seen by the pilots on their instruments.
TAP TP1240 approach into Prague
Flight TP1240 was vectored for an ILS approach to Runway 06 at Václav Havel Airport (PRG).
The published procedure requires aircraft to maintain a minimum altitude of 4,000 feet until reaching the Final Approach Fix (FAF) located 8.8 nautical miles from the localizer “PH”. The Minimum Safe Altitude (MSA) in the sector traversed by the aircraft is 3,600 feet.
At 10:15:25 UTC, Flightradar24 data shows the aircraft turning inbound while passing the published Initial Approach Fix (IAF) BAROX. The altitude was approximately 4,770 feet MSL (4,500 feet at 1013 hPa).
The aircraft then descended steeply. Flightradar24 data indicates a vertical speed of more than 3,000 feet per minute. The aircraft also sped up. The highest recorded ground speed in the descent was 311 knots.
At 10:16:17 UTC, the ADS-B signal reveals the lowest altitude reached: 2,645 feet MSL (2,375 feet). The position was 49.9809°N, 13.8273°E. According to Google Maps terrain data, the ground elevation at this location is approximately 1,700 feet. That places the aircraft just 945 feet above the ground at its lowest point. Czech authorities cited a figure of approximately 1,000 feet above ground, which aligns closely with the ADS-B data available to Flightradar24.
Recovery and safe landing
At 10:16:18 UTC, one second after the lowest recorded altitude, a climb was initiated. The aircraft was at 2,670 feet (2,400 feet). The rate of climb was immediate and steep.
By 10:16:50 UTC, just 32 seconds later, the aircraft had climbed to 5,770 feet (5,500 feet), still tracking northeast towards the airport. According to the authorities, ATC had detected the altitude deviation on radar and issued instructions to the crew to stop the descent and climb.
At 10:17:21 UTC, the crew commenced a left 360-degree turn, descending towards the target altitude of 4,000 feet MSL, and repositioning the aircraft properly for the ILS approach into Runway 06. The aircraft then maneuvered to intercept the localizer from the right side.
At 10:22:52 UTC, TP1240 intercepted the ILS localizer “PH”. At 10:27:06 UTC, the aircraft touched down safely on Runway 06.
The investigation is ongoing
The Czech Air Accidents Investigation Institute is leading the investigation. Deputy director Josef Bejdák confirmed that radar systems detected the deviation and that the crew responded to ATC instructions. He added:
“Our Portuguese colleagues sent us the data from the so-called black boxes, which are currently being analysed and compared with the data obtained from air traffic control.”
We will continue to follow developments as the Czech authorities work to establish the full sequence of events and contributing factors.
Playback TP1240 on Flightradar24
The full approach track and altitude profile for this flight is available on Flightradar24: TP1240 – January 17, 2026.
Note that altitude readings displayed while using our playback function shows altitude based on standard altimeter setting (1013.25 hPa/29.92 nHg). In reality, aircraft navigating closer to the ground will use a local pressure setting (most commonly QNH) specific for that area. This will more often than not differ from the standard value, resulting in a difference in actual versus displayed altitude above the mean sea level. Altitude values in this text have been compensated for ambient pressure. Meanwhile, (altitude within brackets) in this text refer to the raw ADS-B data referencing a setting of 1013 hPa.
For more information, please refer to this helpful blog on how to understand altitude values on Flightradar24.
