What happened
On February 25, 2018, a Boeing 737 700, registration OY-JTY, was performing a commercial passenger flight from Aalborg, Denmark, to Tenerife Sur-Reina Sofia, Spain. Upon reaching the destination at GCTS, air traffic controllers instructed the flight crew to enter a holding pattern because of heavy traffic and prevailing weather conditions.
During this period of delay, the crew evaluated their fuel reserves and determined that they no longer had sufficient fuel to wait for an approach at Tenerife. Consequently, the crew decided to divert the aircraft to Las Palmas/Gran Canaria (GCLP). However, while approaching GCLP, the crew received further instructions from air traffic control to enter another holding pattern. After calculating the impact of this second delay, the crew determined that their fuel upon landing would fall below the legal minimum. The pilot subsequently declared a Mayday emergency. The aircraft successfully landed at GCL and concluded the flight with less than minimum required fuel.
The investigation
The Danish Accident Investigation Board (AIB) was notified of the incident by the Danish authorities in late February 2018. Following a preliminary safety investigation, the AIB coordinated with the Spanish aviation authority (CIAIAC), which took over the primary investigation. The AIB concluded its involvement after establishing the sequence of events involving the two separate holding patterns and the subsequent fuel calculations made by the crew.