RELATED: Never Do This Before Takeoff, Flight Attendant Warns. For almost two years, American and JetBlue have been partners in the Northeast region under a partnership called the Northeast Alliance. Through it, both carriers have been able to amp up their presence in the major metros of both New York and Boston by adding more flights and more routes and simplifying connections—which has been a boon for travelers, too. Late last year, the carriers rolled out reciprocal loyalty benefits, such as one that allowed passengers to redeem AAdvantage miles for JetBlue travel. Now, the two airlines have just announced a new round of benefits that represent major upgrades for elite flyers. They go into effect today. Beginning today, all American Airlines status members will get access to JetBlue’s extra-legroom Even More Space seats at no extra cost when check-in opens 24 hours before flight departure time. The same benefit also applies for JetBlue’s Mosaic elites flying on American; elite flyers will now be able to choose Main Cabin Extra seats at no extra cost. A Jetblue news release details the positive changes. RELATED: Never Ask for This One Favor on a Plane, Flight Attendants Warn. Further, top-tier American Executive Platinum and Platinum Pro elites, as well as JetBlue Mosaic members will be permitted to make same-day confirmed flight changes when flying with either airline. That means Advantage status members Platinum Pro and higher can now access same-day changes when traveling on JetBlue-operated flights. JetBlue Mosaics will continue to benefit from no-cost, same-day changes on American-operated flights. RELATED: For more up-to-date information including travel news and advice, sign up for our daily newsletter. Also starting next month, according to an American Airlines news release, Admirals Club members traveling on JetBlue will be able to access Admirals Club lounges, including the new one at LaGuardia airport. American’s Admirals Club lounges are membership-based lounges with appealing amenities like included food and beverages, Wi-Fi, business centers, and kids’ rooms.ae0fcc31ae342fd3a1346ebb1f342fcb “American and JetBlue are committed to delivering a seamless travel experience to customers through our Northeast Alliance,” American Chief Customer Officer Alison Taylor said in the release. “Part of that dedication includes making travel even more enjoyable for our loyal members, who inspired this opportunity. We look forward to their feedback about this chance to elevate their travel across American and JetBlue.” Beginning this summer, the Northeast Alliance will offer nearly 500 daily departures from the three major airports in the New York metro are, as well as 200 daily departures from Boston. As part of the growth related to the alliance, American plans to launch new nonstop service between John F. Kennedy International Airport and Hamad International Airport in Doha, Qatar, in June—which will make it the only U.S.-based airline to offer flights to the Middle East destination. JetBlue also plans to launch its first-ever Canadian route with new nonstop service between New York’s Kennedy airport and Vancouver in June. RELATED: Never Forget to Do This After Boarding, Flight Attendant Warns.