Alaska Airlines on Monday applied for federal approval to offer nonstop service between Portland International Airport and Reagan National Airport in Washington, D.C., as well as from San Diego to Reagan National. The airline also lined up heavy-hitter support from members of the Washington and Oregon congressional delegations and launched a campaign on its website that urged customers to write letters to the U.S. Transportation Secretary Ray LaHood in support of its application.In an unusual process that applies only to a few U.S. airports, Congressional action is required to add flights to Reagan National. Congress last month approved the addition of four new nonstop flights longer than 1,250 miles, and Monday was the filing deadline to win those four new slots. Alaska, proposing one daily nonstop, was the only airline requesting new service connecting Portland to Reagan National.United Airlines offers nonstop service between PDX and Dulles International Airport in Virginia, about 25 miles from downtown Washington.The Port of Portland has endorsed Alaska’s request.“There are limited opportunities at Reagan National,” said David Zielke, Port of Portland general manager of air service development. “Alaska is the carrier with the most strength in our market. It’s the perfect match for us.”Lisa Nisenfeld, president of the Columbia River Economic Development Council, joined Washington’s political leaders in supporting such new service.“Southwest Washington businesses would benefit from better access to our nation’s capital and the East Coast’s thriving technology industry,” Nisenfeld said in a news released issued by the state’s entire political delegation. “A single, direct flight from Reagan National Airport near Washington, D.C., to Portland will make this region more accessible and attractive to businesses, helping to grow our regional economy.”Alaska is the largest carrier serving PDX, with more than 625 weekly flights. Zielke said the abundance of travel connections on Alaska would enhance the value of the nonstop service to Reagan National.