PORTSMOUTH, N.H. – Free parking, inexpensive fares and direct flights are drawing some Maine passengers to a New Hampshire airport.

Pease International Tradeport in Portsmouth, N.H., is proving so popular with travelers that the airport is planning to expand its service next month.

Pan Am, the only major carrier to use Pease, offers direct flights to Sanford, Fla., 20 miles from Orlando. It also offers flights to several other U.S. destinations from the New Hampshire airport.

But Florida is among the most popular flights with travelers, many of them from Maine.

Maine’s largest airport, the Portland International Jetport, doesn’t offer any direct service to Florida and bargain fares must be booked months in advance. About 21 percent of all outbound jetport passengers are headed to Florida.

While a coalition of business and airport officials has been trying to recruit an airline to begin nonstop jet service between Portland and Florida, industry analysts have said the group faces a tough, uphill battle.

And some passengers say they’re not willing to wait.

“It would be a lot more convenient to have a flight straight through, instead of being in an airport somewhere I have no interest in being,” said Trudy Young of Ocklawaha, Fla., whose family lives in Maine.

Another reason some Mainers are crossing the border to Pease is the fare prices. Consider ticket prices for flights that were available Sunday to Florida: Pease to Florida, returning Saturday, cost $284 round trip. A similar flight for one person from Portland to Florida was priced at $465.

The Pease airport offers the added bonus of free parking.

Pan Am, which began its Florida trips in October 1999, is the only big airline at Pease. As of Feb. 14, it will expand to 10 flights a week from New Hampshire to Florida.

“We are seeing a lot of demand, so we are expanding our flights,” said Dan Fortnam, Pan Am’s vice president for marketing.

The airline also flies from Pease to Chicago, Philadelphia, St. Louis and Bangor.