When it comes to ranking the largest airlines, the top four U.S. airlines have changed little in the past decade. However, one area of evolution has been the prominence of the ULCC. With Allegiant being the only true ULCC from birth, Spirit, Frontier, and now Sun Country have joined the ranks of ultra low fares, and extra charges for everything else. Yet it is this model of un-bundling that ... The largest tankers transiting Canadian waters are Ultra-Large Crude Carriers (ULCC) (350,000 – 550,000 DWT), which transit the east coast of Canada. ULCCs are the largest tankers in the world and they can carry up to 4 million barrels of oil.