A Delta Air Lines flight arriving at the Portland International Jetport early Saturday morning was diverted to Boston because of scheduled runway maintenance, a jetport official said.

The diversion prompted complaints from some passengers, who couldn’t get to Portland until later in the day.

Jetport director Paul Bradbury said the airport’s main runway was closed overnight to repaint the markings. The last flights are due in shortly before midnight, and the main runway closes so that workers have time to complete the work, he said. When a late flight is delayed, there is some flexibility, but if the flight comes in after 12:30 a.m. it’s too late and the runway must be closed, Bradbury said. The Delta flight from Atlanta to Portland was scheduled to arrive at 11:55 p.m. but was delayed and would not have arrived in Portland until after 12:30 a.m., Bradbury said.

Bradbury said Saturday was the third time since the maintenance began in July that planes had to be diverted from Portland to Boston.

“There is no good time to close a runway, but overnight is the best time,” Bradbury said. He said the work started in early July and is expected to be completed by next week. “We certainly apologize to the passengers who were impacted.”

All airlines are notified at least 15 hours in advance of any scheduled work, Bradbury said.

Passengers complained to the Portland Press Herald about being stuck in Boston until Saturday morning because no buses were available. Some rented cars, took a bus in the morning or caught a late Saturday morning flight to Portland.

Ross Greene, who was returning to Maine on the flight from Atlanta, said passengers didn’t know they were being diverted to Boston until they were partway through the flight.

“It was an extraordinary inconvenience for everyone,” said Greene, who stayed overnight in Boston. “It was a bad scene all around.”

He said he was given a hotel voucher by Delta and air miles.

Bradbury said there is a shorter runway, the north-south runway, available for late-arriving flights. But depending on how well the aircraft performs when landing on short runways, sometimes pilots will divert to Boston rather than attempt to land on the north-south runway, he said.

Delta communications officials did not respond to a request for comment Monday.

Bradbury said any refunds to passengers would be handled by the airline.

He said during the past several years, airlines have become more sophisticated in how they route planes, and as a result, the Portland airport is seeing more flights coming in later and starting earlier. The first flights are about 5:30 a.m. Bradbury said the expanded schedule puts the squeeze on when the jetport can complete its scheduled maintenance.

Joe Lawlor can be contacted at 791-6376 or at:

jlawlor@pressherald.com

Twitter: joelawlorph