AMSTERDAM (Reuters -Dutch airline KLM said Thursday it would suspend ticket sales from Amsterdam Schiphol Airport until Monday due to congestion caused by a shortage in security staff.

The third-busiest airport in Europe, Schiphol has seen lines stretch onto the streets over recent weeks. Many travelers have had to wait hours for security clearances and many are now unable to fly.

Gerrie Brand, spokesperson for KLM said that KLM has halted ticket sales on flights departing up to Sunday due to Schiphol’s security issues.

Brand explained that the ticket limit was required to provide accommodation for those who were unable to fly due to chaos at Schiphol.

Air France-KLM, the Dutch branch of the airline group Air France, said it would offer customers with tickets on flights departing in the next three day the chance to modify their flight plans.

Schiphol said Thursday that it plans to increase security staff in the coming summer holidays. Additionally, Schiphol will work closely with airlines to plan flights more efficiently during busy weeks.

Airport said that it had been in negotiations with unions to increase security worker wages.