The blitz to promote Plymouth’s 400th anniversary of the landing of the Pilgrims is underway, with two major airlines and three cable channels scheduled to show a 60-second video in May, focusing on the town’s history and its upcoming celebration plans. “It’s a kind of ‘save the date’ spot that will be seen potentially by close to 150 million viewers,” said Denis Hanks, executive director of the Plymouth Area Chamber of Commerce and Plymouth Economic Development Foundation. Hanks said the video will be shown on US Airways and American Airlines flights and on Bravo, CNN, and the Travel Channel. Local planning committees are also hard at work on other promotional efforts. Surveys have been sent to 75 museums in the U.S. and Europe to see whether they would be interested in hosting a 3,000-square-foot traveling exhibit on the Pilgrim and Wampanoag history, Hanks said. The exhibit is being produced by Content Design Collaborative of Scituate, and is expected to be ready to go on the road beginning in 2017. Plymouth will celebrate the 400th anniversary in 2020.