Air traffic controller work stoppages last month in France, Italy, Spain, Portugal and Hungary will likely continue from time to time in these and other European countries, although they are not expected to thwart European Union plans to create a standardized “single sky” ATC system. Controllers fear that combining ATC services under a single, standardized entity would cost them jobs and open the door to privatization, which they say could put profits before safety. EU officials say that controllers’ concerns are groundless and the single-sky concept remains in the works.