Major airlines worldwide were placing significant orders for commercial jets to modernize and expand their fleets. Traditionally, prominent names like Delta Air Lines, American Airlines, and Southwest Airlines in the United States, alongside international carriers such as Emirates, China Southern Airlines, and IndiGo, had been active in ordering aircraft. However, the dynamic nature of the aviation industry means that this landscape may have shifted. It's advisable to check the latest industry reports or news updates to get the most accurate and up-to-date information on which airlines are currently leading in commercial jet orders.