Traffic at Honolulu International Airport returned to almost normal yesterday, one day after the worst disruption since the 9/11 terrorist attacks.

There were at least two canceled flights yesterday morning as workers continued to deal with the effects of Sunday's earthquake, which triggered power outages around the state.

Air traffic began to clear up late Sunday night after nearly 12 hours on limited backup power that led airlines to cancel more than 80 interisland and Mainland flights.

Neighbor Island airports recovered faster, with several airports maintaining relatively smooth operations on Sunday because the power stayed on or because generators were enough to power security and ticketing systems.

The ordeal, however, of catching a flight to or from Honolulu on Sunday ranged from minor irritant to major frustration because airlines made varied judgment calls that resulted in flight delays for some and cancellations for others.

For instance, American Airlines flew only two planes out of Honolulu Sunday, and canceled six other departures along with eight scheduled arrivals.

Japan Airlines completed all six of its Sunday arrivals and departures, the last one of which left about 8:30 p.m. after a seven-hour delay compounded because the flight originated on the Big Island and stopped in Honolulu before leaving for Japan.

United Airlines on Sunday canceled 11 flights, but completed 16 inbound flights and 14 outbound flights.

Aloha Airlines canceled just four interisland flights out of roughly 100, and made all eight of its Mainland flights.

Hawaiian Airlines canceled 41 of 116 interisland flights, but made all of its 32 Mainland flights. Hawaiian said it consolidated interisland flights so it could accommodate all passengers who came to the airport.

It's expected to take a few days for all passengers who suffered cancellations to complete their travel on rebooked flights, during which time airports are expected to be slightly busier than usual.

Scott Ishikawa, state Department of Transportation spokesman, said airport officials let airlines make the call on whether to cancel flights and said the airport was never closed.

There was roughly an hour from when the power went out about 7:30 a.m. until emergency generators kicked in to run essential operations such as runway lights, some airport terminal lighting and jet fuel pumps.

Left without power were most ticket counters, security scanners, baggage carousels and jetways connecting gates to planes — operations that delayed passenger processing.

"With no power at the TSA checkpoints, no power at the loading bridges, no power to the baggage-handling units, it was very difficult to get things from here to there, and that's what caused the problem," said Transportation Director Rod Haraga, who spent a good part of yesterday morning greeting passengers.

Some airlines canceled most flights while others kept cancellations to a minimum and adjusted to delays.

Aloha spokesman Stu Glauberman said the carrier had its own backup power at an operations control center from which it relayed information to check-in personnel at the airport. Aloha also had use of an elevator to move luggage.

"We flew all day, and we flew roughly all of our flights," he said, adding that the airline carried some passengers for canceled United and Northwest flights.

A go! representative could not be reached yesterday, but the startup interisland airline said on its Web site that operations "may be sporadically interrupted" because of the power outages.

Hawaiian spokesman Keoni Wagner said about 40 percent of Hawaiian's Sunday flights were on time. Delays ranged from a few minutes to a few hours. One Hawaiian flight to Sacramento, Calif., was 11 hours late, while more than one waited on the tarmac for more than a couple hours after arriving in Honolulu because portable stairs to unload passengers were in short supply.

Nearly all airlines resumed normal or close to normal operations yesterday.

Hawaiian reported six long-haul flights faced delays of a couple of hours yesterday because of delays on Sunday.

United said it was flying bigger aircraft on some Hawai'i flights to accommodate passengers who missed Sunday flights, and that it didn't anticipate any other schedule changes.

American said it canceled two flights scheduled to arrive in Honolulu early yesterday morning because the airline couldn't confirm that power to the airport was restored before departure. Six other American flights to Honolulu took place along with eight departures.

Delta Air Lines spokesman Anthony Black said the carrier operated its normal Monday schedule of nine arrivals and seven departures and that there were available seats on flights.

On Sunday, Delta canceled three of seven in-bound flights and two of seven outbound flights. "We should be able to accommodate most people (who missed Sunday flights) if not today, then tomorrow," Black said yesterday.

Transportation director Haraga said that not since the 9/11 terrorist attacks has there been so much disruption at Honolulu Airport.

A 12-hour power outage on O'ahu in 1991 created a similar situation but resulted in minimal delays and no flight cancelations largely because security screening was less intense and required far fewer electronic machines.

At the time, the Transportation Department explored beefing up its backup power system but did not make any major expansion.

Ishikawa said it's not feasible to have generators capable of powering the entire airport, which consumes 14 megawatts of power at peak-hour usage — more power than what's generated for Lana'i (10 megawatts) or Moloka'i (12 megawatts). But the department will explore possibly installing more generators that could run security screening machines, ticket counters and jetways.

"I think it will be discussed during the post-crisis analysis," he said.

Reach Andrew Gomes at agomes@honoluluadvertiser.com.