British Transport Minister Mark Harper announced that resolving the widespread flight disruption to and from the country will take days, after air traffic control systems experienced a technical issue. Authorities canceled or delayed hundreds of flights on Monday, one of the busiest travel days of the week, after air traffic controllers had to switch to manual systems. Harper added that government officials do not believe the technical problem was caused by a cyberattack. He told the BBC on Tuesday, "There will be some impact today, and I think it will continue for a few more days as airlines get their aircraft and services back to normal." Heathrow Airport, the busiest airport in Britain, advised travelers to check with their airlines before heading to the airport on Tuesday. Airlines reported that they were making changes to their flight schedules in an attempt to transport as many passengers as possible, but some planes and crews were not located where they were supposed to be. British Airways stated, "We are doing everything we can to get affected customers on their way again."