Three weeks after the opening, Felipe Angeles International Airport (AIFA), 28 miles (45 km) north of the current Mexico City hub, was still under construction.

The teething problems risk embarrassing President Andres Manuel Lopez Obrador, who made the airport a key project of his presidency, and giving ammunition to the opposition that have long criticized the new airport as a vanity project.

Chain-link fences covered with green tarps lined the entrance to the airport, and dust painted the sky a reddish hue as construction crews continued excavation.

The reality contrasts starkly with the pitch sold by Lopez Obrador, who called it "one of the best airports in the world" ahead of the inauguration.

The leftist rattled investors when he canceled his predecessor's $13 billion partially built airport before even taking office just over three years ago, arguing that the project was riddled with graft, too costly and poorly located.

Instead, he ordered the Army to build a commercial airport on the grounds of the Santa Lucia military air base.

Lopez Obrador inaugurated the airport on March 21, the birthday of 19th century Mexican hero Benito Juarez and ahead of a recall vote on the president's rule, which he handily won despite low voter turnout.

"I think the airport is 100%. It's completely finished," Lopez Obrador said at the grand opening.

As well as the uncompleted construction work, the airport also suffers from congested roadways linking it to the city and will not have a train connection until next year. For the moment, the airport does not allow pick-ups through ride-hailing services.

A new highway connection to the airport is still under construction, though one employee said what had been built cut her commute time in half.

TOURISTS ARRIVE, BUT NOT TO TRAVEL

Of the 14 arrivals and departures confirmed at AIFA that day, compared to the close to 900 daily flights at the main Mexico City International Airport, a handful were military flights, according to flight records.

Since its opening, the AIFA has averaged around a dozen flights a day, flight records show. Around 2,000 passengers use the airport a day, presidential spokesman Jesus Ramirez told Reuters. The AIFA estimates that it will serve 2.4 million passengers this year and double that in 2023, he said.

The AIFA has yet to appoint a spokesperson, officials told Reuters, and the Army and Mexico's Transportation Ministry had no immediate comment for this story.

Inside the new airport, check-in booths stood empty, even as Mexican carriers Volaris, Aeromexico and VivaAerobus as well as Venezuela's Conviasa have announced routes to and from here.

An airport employee who works with the airlines said flights using AIFA were estimated to cost about half of those to and from the original Mexico City airport due to a lower airport usage tariff and government incentives.

Volaris told Reuters that flight costs would be lower, though it said it was not receiving subsidies. The other airlines did not comment.

The airport should at some point have two commercial runways, public construction plans show, though only one is currently in operation.

"Being able to land two planes at once or have two take off at the same time ... not even the Mexico City International Airport has that," said Victor Manuel Pena Chavez, an aeronautical engineering professor at the National Polytechnical Institute.

Past security, staff worked at a Krispy Kreme stall and a Starbucks, while a smattering of storefronts - such as a Mexican-themed gift store and a pastry shop - had already opened. Most spots remained shuttered, plastered with "coming soon" signs.

By late afternoon, plenty of people were milling about the 3,800-acre grounds, though not to travel.

They were curious neighbors or employees on their day off, families that stuck around as the sun went down, hoping to see the delayed Aeromexico flight land.

In the almost four hours that a Reuters journalist spent at the airport, the plane was the only one seen occupying the runway, which flight records confirmed.

"Once we get to mid-year, I really hope there'll be more flights," one of the employees said.

(Reporting by Kylie Madry; Editing by Anthony Esposito, Alistair Bell and Mark Porter)

By Kylie Madry