Basel airport is closed after a light aircraft reportedly crashed while attempting to land.
The plane, thought to be Piper Pa-34 HB-LSD from Nuremberg, was reportedly attempting to land in the fog.
Flights at EuroAirport Basel Mulhouse Freiburg, located about 3.5 km northwest of Basel, are being diverted.
The airport tweeted: "Crash at airport, Airport closed."
Hundreds of Arsenal fans attempting to get home are stranded at the regional airport, close to the border with both France and Germany.
Supporters of the London club are returning from the city after their side's Champions League win.
Basle 1-4 Arsenal: Lucas Perez's hat-trick secures win in Basle
Arsene Wenger's men beat Basel 4-1 on Tuesday night courtesy of a Lucas Perez hat-trick and an Alex Iwobi effort.
British Airways said its 5.27pm BA749 flight to Heathrow was cancelled.
A BA spokesman said: "We are looking after customers and re-booking them on to alternative flights to minimise disruption to their travel plans."