A bus picks up passengers bound for gates located in other terminals at Kansas City International Airport in Kansas City, Mo., Wednesday, Nov. 1, 2017. (AP Photo/Orlin Wagner)

KANSAS CITY, MO. — After years of contentious debate, voters in Kansas City, Missouri, on Tuesday overwhelmingly approved a plan to spend $1 billion to replace the current layout of Kansas City International Airport with a single terminal.

The measure was passing by about a 3-to-1 margin with most votes counted late Tuesday.

Supporters, including a majority of city officials and business leaders, promised voters that the new terminal would be paid for by the airlines and user fees, not tax dollars. They contended the current 45-year-old design with three, horseshoe-shaped terminals is outdated, does not meet post-9/11 security requirements and gives an embarrassing first impression of Kansas City to travelers and corporate officials who might be considering moving to the city or expanding their businesses there.

Mayor Sly James and other supporters argued that a more modern airport would help the area’s economy and likely lead to more direct flights, and perhaps some international flights, out of Kansas City. Airline officials did not promise to add flights but generally supported the single terminal because the layout would be able to handle larger passenger jets better than the current configuration. And supporters said the single terminal would be more comfortable for travelers, by providing more retail options, bathrooms and more efficient security checkpoints.

Opponents, which were loosely organized but vocal, were skeptical that taxpayers would not eventually have to pay in some way for the project, either through taxes or higher ticket prices. They promoted plans to redesign the current layout, which they said would cost millions less than the single terminal while addressing some of the current airport’s deficiencies. They said the redesign would retain the airport’s convenience, while providing better security and more amenities.

Maryland-based Edgemoor’s initial drawings for the new terminal show an H-shaped structure with two concourses and 35 gates. Arrivals and departures would be on separate levels, with curbside service for both, more efficient parking, more retail and a two-story fountain.