A new air traffic control facility in Swansick, Hampshire assumed control of flights over England and Wales last month, but expected heavy traffic over Easter, the second busiest travel weekend of the year, has officials concerned that the new facility may have trouble keeping up. The facility opened during the slowest period of the year and controllers haven’t yet been tested with crowded traffic. Flights could be delayed if minor disruptions occur. The facility is the largest in the world and is designed to handle 6,000 flights a day in summer.