Delta Air Lines has altered its boarding process to minimize the need for travelers to pass one another when getting to their seats. The carrier's main boarding process will have travelers called by rows, starting from the back and working forward, using the spaced boarding process that Delta introduced earlier this month. Delta still will offer pre-boarding for passengers who need extra time and assistance, and travelers in premium cabins as well as Diamond Medallion members can board anytime during the process. The boarding process will be in place through at least May 31.