Due to staff shortages, London Heathrow Airport was unable to handle numerous flights on Monday. These had to be canceled on the instructions of the airport. About 10.000 passengers are affected.
The Heathrow Airports Group justified the decision by saying that there were significantly more passengers on site at short notice than could have been handled. Therefore, some airlines that use Terminals 3 and 5 were "asked" to cancel 61 connections at short notice. The providers were also asked not to rebook the affected travelers on other flights that will be operated from Heathrow on Monday.
This means that around 10.000 travelers are stranded at the UK's largest airport alone and it gets worse: The airport believes that passengers will not receive any compensation, as the cause of the cancellations is said to be outside the airlines' sphere of influence.