If it's a business trip, Flyers vs. Bruins, or your son's birthday, and you live in the Philadelphia region, it just got cheaper to fly to Boston.

Customer-friendly and low-fare JetBlue Airways began five nonstop flights to Boston on Thursday, providing another choice on a popular route and reducing ticket costs.

JetBlue, the dominant airline in Boston with 100 daily flights, is taking on US Airways Group, which now has a lock on the Philadelphia-Boston market.

JetBlue hopes to succeed where three other airlines did not, by winning over business travelers with cheaper fares and offering inflight amenities: leather seats, more legroom in the coach cabin, free live TV and satellite radio, unlimited free snacks, and a free first checked bag.

US Airways, with a hub in Philadelphia and an average 17 daily flights to Boston, was already matching JetBlue's lower fares on some flights on its website.

Whether JetBlue can make money in Philadelphia, and eventually add flights to other cities, will depend on whether Philadelphia travelers who belong to US Airways' Dividend Miles club - and accrue travel miles toward free trips - will choose JetBlue over US Airways.

If ticket prices are the same, will enough passengers fly JetBlue? Southwest, AirTran, and Delta all dropped the Boston-Philadelphia route because they could not compete successfully against US Airways.

"JetBlue likes to find markets that have really high fares where we can make a difference," said JetBlue senior vice president Marty St. George.

"We're very excited about entering the market. If the results in Philadelphia are like what we've seen in Baltimore, Washington National airport, and Newark, it will be a very successful route for us," said George, who with Philadelphia International Airport CEO Mark Gale and deputy mayor for transportation Rina Cutler, stepped off the first flight from Boston at 9:15 a.m. to cheers and a water-cannon salute on the airfield.

"We're thrilled to have JetBlue as part of our family," Gale said. "We chased JetBlue for several years, trying to get them to come here. And we finally convinced them - it took about 432 cheesesteaks!"

Cutler said the new service would be a plus for travelers, help stimulate the economy, and "promote the city's goal of offering convenient, affordable, and customer-friendly air service."

JetBlue said its entry in the Boston-Philadelphia market has decreased the "lowest structured fares" about 40 percent. Before, customers who booked "advance off-peak travel" paid about $236 for a roundtrip; now they could pay as low as $86, a decrease of 64 percent, the airline said.

For those who book roundtrip flights at the last minute, the lowest possible fares have dropped 28 percent, or about $150.

A check on US Airways' website Tuesday for travel to Boston on Wednesday, one day before JetBlue arrived, listed an $816 roundtrip nonstop coach fare. The roundtrip fare on the same flights Friday, a day after the new service, had dropped to $308.

Airfares constantly change, depending on when you buy, when you fly, and how full the plane is.

Here are examples from JetBlue's website: If you want to fly to Boston this Memorial Day weekend, you'll pay $204 one-way Friday and Saturday, with a $154 return ticket Sunday and Monday.

The cheapest days to fly on JetBlue to Boston are Tuesdays, Wednesdays, and some Saturdays, with $39 one-way fares this summer.You can get to Boston for July 4 for $39 on July 2 and 3, with a $79 return flight Sunday, July 7, if booked now.

"I often fly JetBlue. I just think it's the best airline," said Boston passenger Pat Gaffey, on the inaugural flight to visit her daughter in Philadelphia. "They take very good care of you. It's clean. The prices are right. They allow you to check a piece of luggage. The people are very nice."

Why does JetBlue think it can succeed against US Airways here when three other airlines failed?

"So many of our corporate customers in Boston came to us and said, 'Please, we need you to fly this route because our fares are too high,' " George said. "We've got a base of current business customers in Boston who are already committed to fly us."

"We're not going to take anything for granted," he added. "We recognize that US Airways is a very effective competitor."