Today an Air India flight Ahmedabad to London  lost contact with air traffic control over Hungarian airspace,  leading to a fighter jet scrambling after it. The flight had 249 passengers and crew on board. In military parlance, scrambling is the act of quickly getting military aircraft airborne to react to an immediate threat, usually to intercept hostile aircraft.

The jets escorted the flight till it regained the communication and finally it landed safely at the London Heathrow airport.

As per source.