American Airlines canelled more than a hundred flights during the day and several airports in the United States barely functioned, stranding thousands of passengers.
"It’s a mess, to put it mildly," said Tim Wagner, spokesman for the American Airlines.
Worst hit destinations were New York's John F.Kennedy and LaGuardia airports, Detroit and Cleveland.
The Federal Aviation Administration said airports were reeling under the blackout. Security screening machines have stalled and fuelling aricraft was proving difficult.
"Once power is fully restored to those airports, from that point it is a matter of four to six hours before flights begin operation again," Wagner said.
Other airlines were equally hit and cancelled flights in plenty.
Northwest Airlines had cancelled 216 flights on Thursday and its spokeswoman said the carrier would run a limited schedule on Friday.
It’s a mess, to put it mildly"
-- Tim Wagner, spokesman for American Airlines.
United Airlines has cancelled 60 flights over the past 24 hours.
"There are problems," said United Airlines spokesman Richard Nelson.
"People are having trouble getting to work. It is going to be a while before things are restored at those airports just because you have got to get people there…you don’t have personnel to operate the airports," he said.
European airlnes also warned of disruption in their flight schedules.
British Airways cancelled five flights from London to North America during the day. Virgin Atlantic also announced it was expecting futher disruptions.