LONDON (AP) — Tourists and Britons hoping to go on vacation are enduring another day of travel trouble in Britain after severe weather led to flight cancellations and delays on cross-Channel trains.

A week of extreme heat gave way to thunderstorms Friday, touching off travel delays on Saturday.

Budget airline Ryanair says Friday night's thunderstorms, along with air traffic control staff shortages, led to 14 cancelled flights at Stansted Airport. Other London-area airports — Luton, Gatwick and Heathrow — also warned of delays.

Nats, the UK air traffic control service, says the unpredictable nature of the storms means aircraft are not able to fly their usual routes. The service says the thunderstorms "effectively block large swathes of airspace because aircraft cannot fly through them."

Eurotunnel passengers faced a third day of disruption on the cross-Channel service.