Budapest - Passengers at Budapest's airport faced hours of frustrating delays on Monday - because security staff forgot to close a door.

Operations at Ferihegy International airport were paralysed because passengers on an early morning flight from the Syrian capital Damascus were allowed to mingle with those arriving from Schengen countries, spokesman Mihaly Hardy told the local news agency MTI.

"The Schengen and non-Schengen passengers were mixed up because a service door was unintentionally left open," Hardy admitted.

All flights are subject to significant delays, and the timetable is only likely to return to normal by the end of the day, said Adam Hegedus, a spokesman for the Hungarian national airline Malev.

Though departures from Terminal 2 are subject to delays, no flights were cancelled and arrivals are not affected by the problem, Hardy added.

Hungary joined Europe's open-border Schengen zone in December, 2007. Passengers travelling between Schengen countries do not have to undergo the same rigorous security checks as those from outside the zone. (dpa)