Regulators have largely ignored a series of dangerous incidents in which cockpit windshields in commercial airliners shattered in mid-flight, sometimes forcing emergency landings, according to an American Airlines pilots' group. A pilot who spoke to CNN said the cockpit window on his plane two years ago "shattered like a spider web." Since 2004, at least 10 windshields have had problems on Boeing 757s, mostly the result of wiring problems with windshield heaters that cause smoke to fill the cockpit and sometimes make those windshields crack, according to the National Transportation Safety Board. Four incidents have been on American Airlines planes, the NTSB says. One example was an American Airlines flight from San Juan, Puerto Rico, to Philadelphia, Pennsylvania, made an emergency landing January 30 after the cockpit filled with smoke. The inner pane of the co-pilot's window shattered as the plane came in to land in Palm Beach, Florida. No one died in the incident. The FAA finally issued a proposed airworthiness directive for inspection and corrections to windshield heaters, not just on 757s but also on Boeing 767s and 777s. But the FAA did not address why it has taken this long to address the problem since Boeing flagged it as an issue as early as 2004, the first time the NTSB also took notice. A safety recommendation sent by the NTSB to the FAA in September gives details of the problems, many linked to the wiring of the windshield heaters. The recommendation also mentions promises by Boeing to send out service bulletins and pledges by the FAA to make the Boeing suggestions mandatory.