This story was updated at 1:18 p.m. Thursday.

Air service has returned to Houston's George Bush Intercontinental Airport and hub carrier United Continental Holdings Inc. (UAL) - Get United Airlines Holdings, Inc. Report has been able to ramp up service at a faster rate than it anticipated following Hurricane Harvey.

The carrier will operate 44 arrivals and 27 departures Thursday, spokesman Charles Hobart said.  Early Thursday afternoon, he revised an earlier estimate of 14 departures and 27 departures.

While United originally thought it could serve only hubs, it has also been able to schedule Thursday flights to Clearwater/St. Petersburg, Fla.;  Savannah, Ga. and New Orleans -- cities where schedulers identified a need for additional lift. 

"It will take several weeks to be at full schedule," Hobart said, "We have always said we would start up relatively slowly and work into a more robust schedule.

"Right now, we're focused on getting people into Houston, {people} who have wanted to get there for quite a while and haven't been able to," he said.

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Normally United offers 483 daily departures including 218 mainline departures from Houston, its second-largest hub.

Among the barriers to full operation: Many Houston employees cannot get to the airport. Also, while United has planes on the ground in Houston, those planes require maintenance checks before they can fly after sitting outside in inclement weather.

Hobart said several hundred United customer service agents and fleet service workers from other cities have volunteered to fly to Houston in order to assist in the service restart. That is enabling other workers, who volunteered to fly in before the storm, to return home.

"We have been working throughout the week to reposition crews and aircraft," Hobart said.

On Wednesday afternoon, the airline had planned to restart operations on Thursday, but late Wednesday it saw an opportunity to operate three inbound flights from Chicago, Newark and San Francisco as well as three departures to Chicago, Denver and Newark.

United's hubs, ranked by daily departures, include Chicago, Houston, Newark, Denver, San Francisco, Washington Dulles and Los Angeles.

This article is commentary by an independent contributor. At the time of publication, the author held no positions in the stocks mentioned.