Hungarian authorities reportedly issued their highest alert after the Boeing 777 passed over its border unannounced on Saturday afternoon.
Two Hungarian Air Force Gripenswere scrambled to identify the aircraft which was en route from Dubai to Heathrow.
According to air safety protocol, pilots must make contact with air traffic controllers on the ground when passing from one country's airspace to another.
The Gripens jets reportedly took off before the BA flight made contact with ground control after which theyreturned to their base.