PORTLAND — City officials today held a groundbreaking ceremony to mark the start of the $75 million expansion at the Portland International Jetport, the most ambitious expansion in the airport’s history and the largest construction project currently in Maine.

The project will nearly double the size of the existing terminal, adding 137,000 square feet of space.

Airport officials say the expansion will allow the terminal to handle an anticipated increase in passengers. Currently, there are not enough gates to support another airline. The project will add three new departure and arrival gates, eight new passenger screening lanes and a new baggage-handling system, which will be capable of in-line explosive detection.

A new pedestrian bridge over the road that passes by the entrance to the terminal will allow people to park in the garage and walk directly to baggage and security screening areas.

Councilor Dan Skolnik, chairman of the building committee for the project, said it is gratifying to see the project begin after two years of work on the project’s design and budget. He said the expansion will allow the city-owned airport to be “user-friendly.”

Councilor Cheryl Leeman said the expansion plan is similar to what a city committee she had served on 20 years ago had envisioned.

“My God,” she said as she looked out over the construction site. “It’s pretty amazing to see how the airport has expanded so efficiently and tastefully.”

Turner Construction Company, an international firm with a regional office in Boston, is managing the project. Construction work started on March 15 and is scheduled to be completed by Feb. 1.

The project was originally scheduled for completion last October. But the airport was forced to delay it in fall 2008 because the nation’s financial crisis made it impossible to find a company that would insure the debt. The airport’s original underwriter was Bear Stearns, a global investment bank and securities-trading brokerage that collapsed.

Airport fees and a federal grant will pay for the project.

Funding will come from a $4.50 fee on every ticket. Passengers already are paying the fee, with the revenue going toward debt payments that will soon be retired.

Additional funding would come from rent paid by new vendors in the expanded terminal. The federal Transportation Security Administration is providing $9.1 million for security upgrades.