ST. LOUIS — St. Louis Lambert International Airport held a three-hour open house on Thursday, and officials released new details about a master plan that could transform the aging airport.

A preliminary estimate puts the cost at nearly $45 million dollars per airport gate. The master plan calls for 62 gates, meaning more than $2.7 billion in total.

The airport’s signature domes that were part of the original Lambert Field that opened in 1956 will remain. Almost everything within the airport’s two terminals would change.

A steady crowd filtered through the open house, which featured large poster boards outlining possible changes. They would be more extensive and expensive than Kansas City’s ongoing $1.5 billion dollar airport makeover.

Lambert’s two terminals would be combined into one. There would be one large security checkpoint instead of the current four. Southwest Airlines’ Terminal Two, which opened in 1998, could be converted into another use, such as a hotel.

The short airport drive from Interstate 70 would be greatly extended, so people actually have time to follow the signs. The new single terminal would have 62 gates (up from the current 54) with wider 110 feet concourses (up from 75 feet), providing much-needed room for everything from more connecting flights for Southwest to more shops and restaurants in the concourses for travelers.

John Van Woensel is the vice president of the firm WSP, which is the lead consultant for the new master plan. Woensel told the crowd that none of the changes are possible at Lambert right now.

“Do we want to expand the restrooms?” he asked. “Then, we have to take the restaurant out. If we want to expand the restaurant, then we have no place for passengers to sit to wait on the planes. There’s just no room to do any of those things.”

“Thirty-two percent of Southwest traffic is connecting. We want that to grow more,” said airport director Rhonda Hamm-Niebruegge. “You’re not going to be able to build more parking without this plan. You’re not going to be able to build more concessions, more retail, all of those things that drive revenue that help your cost. When you think about four different checkpoints, that’s costly. You have equipment that’s duplicated. You have the manpower that’s duplicated.”

“It’s time,” said traveler and former airport worker Rosemary West. “I’ve been to several airports. Ours is nice. The people are super, but we need an update really bad, I think.”

With public input, the master plan can be finalized by the Fall. The start of construction would be four at least years away with airport bonds, federal grants, plus passenger and airline user fees, covering the cost.

State and local taxes would not be used for funding.