daa is advising all passengers due to travel today to check the status of their flight with their airline before travelling.
There are reports of a "network-wide failure" across UK air traffic control systems, and engineers are working to "fix the fault".
Travel expert Simon Calder says the system is designed to cope with situations like this:
"Aircraft have contingency fuel so there is no possibility that there's going to be aircraft in the sky running out of fuel. They will declare a diversion. You're gonna see an awful lot of planes touching down in places like Amsterdam."
