Swiss passengers are feeling the knock-on effects of a British anti-terrorist operation that has closed London's Heathrow airport to incoming flights.
Passengers were turned away from Zurich, Basel and Geneva airports on Thursday morning as flights to British destinations were delayed or cancelled after an alleged bomb plot was foiled.
Swiss airports insist that they are coping with the strain, while local carrier Swiss International Air Lines said it has no plans to follow the example of German parent company Lufthansa, which has suspended all its flights into Heathrow.
The Swiss federal authorities say they are monitoring the situation, but have not yet issued any specific security advice.
The dramatic development followed the discovery of a possible terrorist plan to blow up planes flying from Britain to the United States by smuggling bombs on board in hand luggage.
British authorities have arrested 21 people and tightened security at airports, restricting the hand luggage passengers can take on board. No such measures have been taken at Swiss airports.
"We are right now evaluating the situation together with specialists from the federal police," Federal Office for Civil Aviation spokesman Daniel Göring told swissinfo.
"If any additional measures are necessary then we will take them."
Zurich airport said disruption has been kept to a minimum despite British Airways cancelling all six flights to Heathrow on Thursday. The airline has stopped all short-haul flights to and from London.
Swiss has also had to cancel some flights and expects delays to other London destinations.
In addition, low-cost carrier easyJet, which has recently expanded its operations in Switzerland, has cancelled all its flights from the London area - Gatwick, Stansted and Luton.
Staff at Basel airport are coping with the situation where around 500 passengers were affected in the morning (half of them in London expecting to fly to Switzerland), according to spokeswoman Vivienne Gaskell.
"The situation is relatively stable because the cancellations represent a small proportion of our total flight movements," she told swissinfo.
"It is important to keep in contact with the passengers and we are trying with the airlines to find alternative routes if possible."
swissinfo, Matthew Allen
Basel airport operates nine flights a day to London, three of them to Heathrow.
Zurich airport operates 12 flights a day to Heathrow and also flies to Gatwick, London City and Luton airports in the area. British Airways has cancelled all its six flights from Zurich to Heathrow on Thursday.
Geneva airport operates eight daily flights to Heathrow, and also services Gatwick, Stansted, London City and Luton airports.
Brussels airport in Belgium has cancelled all flights into London.