Boeing CEO Dennis Muilenburg acknowledged Wednesday that aviation authorities around the world may not be ready to unground the plane when the U.S. Federal Aviation Administration decides to do so, a move that is anticipated to come sometime this fall. The European Union Aviation Safety Agency could well need until the spring to define what it believes needs to be done to address the 737 MAX's safety issues, a lag that would pose serious problems for Boeing and airlines. A solution that could speed up the process, if at great expense: deciding to add an additional angle of attack sensor (or two) to the plane.