Southwest Airlines (WN, Dallas Love Field) has proposed adding a new clause to its labour contract which would theoretically open the possibility of diversifying its fleet make-up, The Seattle Times has reported.

"We are flying to more destinations that vary in distance, size and seasonality. This change [i.e. the flexibility to add other aircraft types] would allow us to fly aircraft types that are better suited for some of the markets we serve," the LCC said in the proposal.

However, Southwest Airlines said that it had "no current plans to pursue or introduce a new fleet type".

According to the ch-aviation fleets advanced module, the LCC currently operates 754 Boeing narrowbodies, including 513 B737-700s, 207 B737-800s, and thirty-four B737-8s. The last type is currently grounded. The global grounding of the B737 MAX and the high exposure of Southwest Airlines to the event prompted speculation that it might turn away from the single-type B737 fleet in the future.

Southwest said that it analysed the A220s in the past and admitted that Airbus is aggressively offering its equipment, but underlined that a decision to order another type would be "a huge strategic question" and would take years to implement.

The LCC is currently the world's largest operator of Boeing aircraft. It has a further 149 B737 MAX on order from the manufacturer, including thirty B737-7s and 119 MAX 8s. It planned to take a further forty-one units in 2019 on top of the thirty-four already delivered. According to the original plan, the seventy-five B737 MAX would have represented almost 10% of Southwest's fleet by the end of 2019.