Spirit Airlines is planning to open crew bases in Atlanta and Miami this year, according to a note sent to flight attendants that their union sent on Thursday.

The Miramar, Fla.-based discount airline is setting up the new bases for pilots and flight attendants as it staffs up to take on bigger rivals with strong holds on those airports, like Atlanta-based Delta Air Lines and American Airlines, which is the dominant airline in Miami.

Spirit first launched service from Miami International Airport last October and now has 30 nonstop routes from there, making it the second-biggest carrier at the airport, still far behind American Airlines, which has more than 300 daily departures out of the airport this month.

Spirit and fellow budget carrier Frontier Airlines last month announced plans to merge into the country’s fifth-largest carrier. Spirit Airlines spokesman said the crew bases are not related to the combination.

The new bases come after Spirit has been studying for months how to staff more efficiently after crew shortages contributed to more than 2,000 flight cancellations in the middle of last summer.

Spirit, like other airlines, has been scrambling to hire pilots, flight attendants and other staff to cater to the rebound in travel demand.

The airline said it plans to have more than 100 pilots and 200 flight attendants at each new base at first. The note to flight attendants said the bases are expected to open in June.