On 27 February, A Pakistan International Airlines Boeing 777-200 operating Flight PK-786 from London Heathrow to Islamabad lost radio contact for a space of about 50 minutes.
According to reports by The Aviation Herald, ATC first lost contact with Flight PK-786 whilst in German airspace.
After passing into Czech airspace, Czech ATC was also unable to get a response from the crew of the Pakistan International Airlines Boeing 777 after multiple attempts to make radio contact. Czech fighter jets were scrambled to escort Flight PK-786 to the border.
The aircraft continued on its scheduled course at FL370, and subsequently passed into Hungarian airspace. The Hungarian Air Force had already deployed its Gripen fighter jets to intercept the aircraft, as the Czech Air Force had given warning ahead of its arrival.
The PIA Boeing 777 remained uncontactable on radio as it passed over Hungary, and only re-established communication as it crossed into Romania. Communication was finally made with Bucharest Area Control at 20:18 UTC. In total, the aircraft did not communicate with ATC for around 50 minutes as it passed over Czechia, Slovakia and Hungary.
As reported by The Aviation Herald, the crew of the Flight PK-786 did not respond to multiple ATC attempts to restore radio communication. Czech ATC instructed the crew to press ‘ident’ on their transponder.
Presumably, this was an attempt to gauge whether the flight was suffering from a one- or two-way radio failure. Czech ATC also tried to reach Flight PK-786 on guard frequency but both attempts fell on deaf ears and the aircraft proceeded to fly towards Slovakia.
Before the flight left the Czech ATC zone, ATC informed the crew of the next frequencies. It looks like this information was also not received. Going off the fact that radio communication was only restored as the aircraft passed into Romanian Area Control, it looks most likely that the crew of PIA Flight PK-786 was oblivious to the multiple attempts to make radio contact.
This is most likely due to a mixture of inadequate communication skills and training, which meant that radio commands were not understood, and also being tuned into an incorrect radio frequency for ATC over Czechia, Slovakia, and Hungary.