Health union workers were due to walk out on Thursday in a dispute over pay.
Luton Airport says services are returning to normal after an earlier fire alarm.
A 48-hour strike planned by workers on London's Docklands Light Railway from tomorrow has been suspended.
The Rail, Maritime and Transport (RMT) union said talks with the DLR operators had secured an agreement. Workers were due to walk out from tomorrow morning in a dispute over outsourcing and new human resources policies.