Dutch police have arrested 12 passengers after a US flight en route to India had to return to Amsterdam because of a security alert.
Despite the alert no extra security measures are in place at Schiphol
The pilot turned back over German airspace after the crew said a number of passengers on the flight to Mumbai (Bombay) were behaving suspiciously.
Two Dutch air force jets escorted the the Northwest Airlines plane back to Amsterdam's Schiphol airport.
Police are questioning other passengers and crew members.
No further details of the arrests have been given.
Police began questioning several of the 149 passengers on board once the flight had landed.
The airline said flight 42 had turned back after "a couple of passengers displayed behaviour of concern".
It said the same flight would be operating on Thursday, and passengers were being accommodated in nearby hotels.
No extra security measures are in place at the airport.
The threat level at Schiphol had returned to normal, airport spokeswoman Pamela Kuypers said.
The Netherlands' national co-ordinator for counter-terrorism said there was no reason to upgrade the country's terror alert level, which is currently at "substantial", the second-highest of four levels.
Security levels at airports across the world were raised two weeks ago after British police said they had foiled a plot to blow up a number of trans-Atlantic flights.
Several security alerts since then have seen flights diverted, passengers removed or planes searched.
The Dutch secret service said in March that the Iraq war and the presence of Dutch troops in Afghanistan could motivate possible attacks and encourage the recruitment of Islamist militants in the Netherlands.
Earlier this year, a Dutch court convicted nine Muslims of belonging to a terrorist group and planning to attack politicians.
In June 2005, a Dutch court sentenced a 27-year-old radical Islamist to life in prison for murdering the controversial film-maker Theo van Gogh the previous year.