By Tony Owusu Depending on who you believe, air traffic control staffing or airport construction is responsible for United Airlines cancelling dozens of daily flights at Newark Airport through the end of the summer. An already hectic summer air travel season is about to get much more frustrating. Just eight weeks ago, United Airlines was feeling a lot better about the summer travel season, so the company said that it would kick off the largest transatlantic expansion in its history. The airline planned to add or resume 30 flights over the next two months, growing its capacity in the market by …