Accident during flight with a Boeing 737-800 bound for Stockholm/Skavsta Airport

Summary

A passenger aircraft of the type Boeing 737‑800 was enroute to Stockholm/Skavsta Airport at the same time as two JAS 39 Gripen fighter aircraft, flying in a two-ship formation, departed from Linköping‑Saab Airport. In the airspace above Östergötland, the TCAS collision avoidance system generated a resolution advisory instructing the passenger aircraft to perform an evasive manoeuvre in order to avoid a collision with the fighter aircrafts. The passengers were seated with their seat belts fastened, but the cabin crew were in the process of securing the cabin for landing. During the manoeuvre, one of the cabin crew members was seriously injured.

All aircraft involved were being manoeuvred in accordance with the applicable regulations and procedures, and the clearances issued by Air Traffic Control (ATC) were complied with. At no time was there any actual risk of collision.

The investigation concludes that fighter aircraft and other aircraft operating with high vertical speeds cause TCAS to be triggered significantly earlier than in situations involving civil traffic only. Furthermore, neither the TCAS system, the regulatory framework nor ATC procedures are designed to accommodate the interaction between civil and military traffic.

The investigation further concludes that there is a need for additional education and training on the TCAS system.

Causes of the accident

The direct cause of the accident was that the passenger aircraft’s collision avoidance system (TCAS) generated a resolution advisory (TCAS RA) for an evasive manoeuvre because the two fighter aircrafts were approaching with a high vertical speed. The Commander followed the TCAS resolution advisory, resulting in a rapid change in the aircraft’s pitch attitude. This change in pitch attitude in turn caused such pronounced movements in the part of the air­craft where the cabin crew member was standing that the crew member was unable to compensate for them.

A contributing factor at system level was that the Air Traffic Management system does not take into account how the TCAS system handles fighter aircraft with high vertical speeds.

Safety recommendations

SHK submits the following recommendations:

Norwegian is recommended to

• review simulator training regarding TCAS phraseology in order to ensure correct communication (see Section 2.7.1). (SHK 2026:11 R1)

The Swedish Transport Agency is recommended to

• examine whether the handling of TCAS should be included in refresher training for air traffic controllers with a specified periodicity (see Section 2.7.3). (SHK 2026:11 R2)
• to carry out targeted information activities directed at providers of ATC services, in order to increase awareness of how military aircraft operate and the challenges this entails for the interaction with civil traffic in the airspace (see Section 2.7.3). (SHK 2026:11 R3)

The Swedish Armed Forces is recommended to

• examine the need to introduce training on the TCAS/ACAS system for pilots who do not normally operate aircraft equipped with these systems and, where necessary, provide such refresher training (see Section 2.7.4). (SHK 2026:11 R4)