The loss of commercial flights at Arnold Palmer Regional Airport is expected to result in a projected revenue shortfall of as much as $300,000 through the end of this year, a Westmoreland County Airport Authority official said Tuesday. Last year saw more than 100,000 passengers pass through the gate, according to airport authority Executive Director Maurice Haas. Officials said the termination of commercial service created a major hole in the authority’s $5.1 million operating budget. The airport authority laid off 25 employees this spring — about half its staff — following Spirit’s departure. Expenses at Palmer Airport in July totaled more than $405,000.