Allegiant Airlines is pulling service from the airport serving Fort Collins and Loveland — again.

The discount airline promising service to and from Las Vegas and Phoenix blamed the lack of an air control tower at Northern Colorado Regional Airport, again.

A month before commercial air service was to return to Northern Colorado, Allegiant notified customers via email it would not be flying to the airport because its long-awaited virtual tower was not up and running.

"As part of our agreement to schedule service in Fort Collins, Allegiant was given assurances that an FAA-certified air traffic control tower would be in place at the airport this fall, well in advance of our first scheduled flights," Allegiant wrote to customers.

"Unfortunately, circumstances beyond our control have left that promise unfulfilled, much to our frustration. Because we cannot responsibly operate at the airport without a control tower in place, we are left with no choice but to cancel service at this time."

Airport Manager Jason Licon told the Coloradoan the FAA delayed testing of the virtual tower until late January, a decision over which the airport had no control. Airport and city officials had come up with an alternate plan — a mobile tower — that would have had air traffic controllers on the ground to serve as a bridge until January.

"The FAA couldn't certify it, and it's not clear why," said Fort Collins Mayor Wade Troxell.

The airport is owned by the cities of Fort Collins and Loveland and is located just off Interstate 25 in Loveland. Officials learned of Allegiant's decision during an airport commission meeting Monday afternoon.

The announcement is leaving residents like Chris Maguire scrambling to find another flight for his college-student son at Thanksgiving. All Maguire knew Monday afternoon was that his son Shane's flight from Phoenix had been canceled.

Thea Hamm isn't sure what will happen to her mini-vacation to Las Vegas over Thanksgiving. She booked her flight on Sept. 17 and had planned to spend the holiday in Nevada with friends.

"I don't know if we will still go," she said. "I don't want to book out of Denver and have everyone else cancel because it's a pain in the butt."

Hamm checked into flights out of Cheyenne, but they were cost-prohibitive, she said.

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The letter obtained by the Coloradoan via multiple customers is unclear about whether Allegiant is pausing air service from Northern Colorado Regional Airport or pulling out completely.

"We deeply regret this change in plans, and especially the disappointment and inconvenience it will cause customers who were looking forward to flying these routes," the note to customers said.

"Please know that this decision was made in the name of safe and responsible operations. We hope to be able to serve Fort Collins in the future should circumstances change."

Allegiant officials were not immediately available for comment.

The airport's virtual tower is in the testing phase and was never expected to be operational by Nov. 21, when Allegiant was to begin air service four days a week to Las Vegas and twice a week to Phoenix, Arizona.

Instead, the virtual tower was to be tested in tandem with a temporary air traffic control tower installed and manned by air traffic controllers so the remote tower could be tested and evaluated, Licon said.

But with the delay imposed by the FAA, Allegiant made a "business decision," he said. He views the airline's decision as temporary.

"It's better for them to delay and refund tickets one time rather than multiple times if the FAA timeline is not met in January," Licon said. "The airline is trying to be very conservative ... it's a lot easier for them to go with a clean slate at this time."

Testing of the virtual tower will unlock opportunities for future air service, Licon said. "I should hope it would include Allegiant."

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Allegiant and airport officials held a hastily organized press conference Aug. 13 to announce the airline was returning to Northern Colorado, a move that promised up to $8 million a year in economic impact.

Allegiant pulled service from what was then called Fort Collins-Loveland Municipal Airport in 2012 with less than three months' notice, citing the lack of an air traffic control tower. After that, airport officials worked to solve that problem and came up with the first FAA-sanctioned virtual tower in the country.

Instead of air traffic controllers sitting in a tower high above the airport, virtual tower controllers keep their eyes on the bank of monitors at Northern Colorado Regional Airport as cameras stationed around the airport capture a panoramic view of air and ground traffic.

In August, when asked by reporters what assurances the public had that Allegiant would not pull out of the market again, spokeswoman Kimberly Schaefer said there should be "no concerns" about Allegiant possibly pulling out of the airport again. While every market takes time to mature, "we see demand here that more than exceeds what we need to make the routes successful," she said.

Pat Ferrier is a senior reporter covering business, health care and growth issues in Northern Colorado.