HONOLULU -- Airlines on Monday scrambled to get mainland flights back on schedule after a massive backlog at Honolulu International Airport on Sunday.

A power outage following Sunday's earthquake made processing passengers difficult.

Many weary travelers hoping to get back to the mainland spent an uncomfortable night on the hard and cold floor of the Honolulu International Airport.

"It was very tiring and frustrating, but I understood what was going on," Tennessee resident Greg Gillaspie said.

The Gillaspies said the airport sleepover and surprise Sunday earthquake did not rattle their vacation.

"It's just wonderful. It's just beautiful. It was a little scary but when we figured out it wasn't a tsunami. We were going to be OK. We had a wonderful time," Beth Gillaspie said.

Several mainland flights were canceled or delayed on Sunday, leaving a massive backlog.

"So (the flights) are going to have to be made up today or the next couple of days," state Department of Transportation spokesman Scott Ishikawa said.

Ishikawa urged travelers should call the airlines first and make sure they have a flight before coming to the airport.

"We don't want any confusion of someone coming down, not having a flight before they are set to go," Ishikawa said.

A day after Sunday's long lines, there was still some confusion and congestion. At noon, the lines at the interisland terminal snaked outside.

Both Aloha and Hawaiian airlines said that their flights were on time. Aloha officials said that United and Northwest airlines sent some of its passengers over to Aloha to get back to the mainland and they were not ticketed properly.

Hawaiian blamed the long lines on full flights, travelers arriving late and passengers arriving at the airport instead of calling to make changes to their flights.