By Mitch Lipka March 12 (Reuters) - For those who fly in and out of New York airports -- fasten your seat belts for one of the biggest changes in recent memory. Delta Air Lines Inc and US Airways Group are making major alterations to their route maps, with most of the changes effective March 25. Delta will increase the number of its flights by 60 percent and add 100 new flights through New York's La Guardia Airport. US Airways will eliminate numerous routes, but will maintain its Boston and Washington, D.C. shuttles and will fly to Pittsburgh and its hubs in Charlotte, Philadelphia and Phoenix. What's happening amounts to a concession of the valuable New York market by US Airways, says Seth Kaplan, managing partner of the trade journal Airline Weekly. "It's a big deal." Airline experts say US Airways will be shutting its competitive, and therefore less profitable, routes and will focus on its dominant position at Washington, D.C.'s Reagan National Airport. The changes will allow some frequent flyers to better consolidate miles and avoid layovers as well as get new destinations to fly to from LaGuardia. But the overhaul could also result in fare increases on some routes because fewer carriers will be serving the routes. It could also inconvenience customers who live in cities where US Airways is dropping routes but Delta is not adding any. Some other noticeable upgrades on the way: Wi-Fi and first-class service on jets and a $160 million renovation of Terminals C and D at LaGuardia, said Delta spokesman Joseph R. Perone. A second phase of changes is scheduled to take effect July 11. "This is a very significant change. It is a massive number of slots changing hands, and it does remake the landscape," said Brett Snyder, who runs the air passenger site Crankyflier.com. "You lose one player in US Airways but you gain a stronger Delta that's more competitive with United (owned by United Continental Holdings Inc )." WINNERS AND LOSERS The winners: Cleveland, Ohio; Milwaukee, Wisconsin; Dallas and Houston, Texas; and the Canadian cities of Ottawa, Halifax and Montreal. These locations will likely see a significant net gain in flights. Toronto flyers will benefit tangentially. To meet regulatory requirements in the deal between Delta and US Airways (US Airways gets Delta slots at Reagan National Airport), Canadian carrier WestJet will add flights to Canada's largest city. The biggest losers in the change of destinations, according to an analysis by Snyder: Albany, New York; Baltimore, Maryland; Charlottesville, Virginia; Harrisburg, Pennsylvania; Hartford, Connecticut; Ithaca, New York; Providence, Rhode Island; and Roanoke, Virginia -- all of which have lost US Airways flights and will get far fewer or no Delta flights in return. Other cities, including Portland, Maine; Portsmouth, New Hampshire; and Charleston, South Carolina will also see a significant percentage drop in flights to and from New York. Travelers who will be most inconvenienced are those who are heavily invested in US Airways' frequent flyer program. Air travel experts say those customers should ask Delta to give them the same status they had earned with US Airways. Passengers can also leave from Newark Liberty International Airport, where United has a huge presence and is part of the Star Alliance frequent flyer miles group along with US Airways. Kaplan notes that miles can also be earned or used on other Star Alliance airlines, including Air Canada, but not all benefits of high-mileage flyers are reciprocal in the program. For example, you are not entitled to a complimentary upgrade of your seat when flying on another Star Alliance airline. BUSINESS SENSE Airline industry experts say the deal between US Airways and Delta makes sense for both companies. "The route swap between Delta and US Airways will add efficiency and economy to both carriers," says Northeastern University economist Harlan Platt. "This is especially true of Delta whose major investment at LaGuardia needs passengers if it is to make sense." Platt and others noted that passengers could see higher ticket prices in the markets where a single carrier -- whether it be Delta or US Airways -- dominates an airport. For New York business travelers like Glenn Haussman, the impending expansion by Delta is all good news. "I'm very excited. I'm sitting here right now waiting for a flight," he says from his cell phone at the Delta terminal. "For me as a passenger, it makes me very happy." The changes mean convenience and the ability to stick with one airline and build miles, he says. "There will be so many more direct flights," says Haussman, who is editor-in-chief of HotelInteractive.com and flies from New York 25-30 times a year. "This means I won't have to go through Minneapolis. I won't have to go through Atlanta. Consumers really like to fly direct."