WASHINGTON (AP) — Investigators say the crew of the Army helicopter that collided in midair with an American Airlines jet near Washington, D.C.’s Ronald Reagan National Airport may have had inaccurate altitude readings in the moments before the crash, and also may not have heard key instructions from air traffic controllers to move behind the plane.National Transportation Safety Board Chairwoman Jennifer Homendy says the recording from the Black Hawk helicopter cockpit suggests the crew may have missed the key instruction just before the Jan. 29 collision, in which all 67 aboard the two aircraft were killed.