All United Continental flights in the U.S. are currently grounded due to computer problems.
United said in a statement on Wednesday that it is working to resolve the problems, which are related to “network connectivity.”
It is the second time in two months that the Chicago carrier has been hit by major technical issues.
United Continental Holdings Inc. had a temporary halt to all takeoffs in the U.S. on June 2 because of what the airline said were computer automation issues.
Its stock declined slightly in premarket trading.