A Spirit Airlines aircraft landing. AP Photo/Keith SrakocicAmerican Airlines and Spirit Airlines cancelled hundreds of flights Monday.Another summer travel mishap is due to bad weather and reports of a shortage in flight crews.The pandemic has caused a reduction in the ability of airlines to recover.Check out more stories from Insider's business page.It's the summer of vaccine-free travel.Spirit Airlines and American Airlines cancelled 729 flights Monday afternoon, and counting, as bad weather and "operational difficulties" plagued cities throughout the American South.FlightAware reports that 275 Spirit flights were cancelled at the time this article was written. This represents 35% of Monday's scheduled flights by the airline.Spirit tweeted, "We are experiencing operational difficulties in some areas of the network," "Before you go to the airport, make sure to check your email and flight status."According to FlightAware, an additional 159 (or 20% of Spirit's Monday flying) were marked as delayed.Spirit's problems are primarily caused by its main bases in Texas, Florida, and Louisiana. Bad weather, including storms, has been devastating Florida and parts Texas.According to FlightAware, Dallas/Fort Worth International Airport leads the world in flight cancellations, delays and delays. There were 138 cancellations, 240 delayed flights, and 35% of Monday flights at the airport.Fort Lauderdale International Airport is a lower-ranking airport, but it still reports 39 cancellations and 85 delays in departures. Another Spirit base is Orlando International Airport. There are 37 cancellations and 129 delays.Spirit asks passengers who are experiencing problems to use its live chat feature on its website for assistance with bookings.Insider was told by a Spirit spokesperson that they are working round the clock to get things back on track after some travel disruptions this weekend caused by a series weather and operational problems. "While we had to cancel some flights, the majority of flights remain as scheduled."Continue the storyAlthough Spirit had made strides towards becoming a more punctual airline prior to the pandemic, its performance has been slowed in recent months. Spirit was ranked 10th among US airlines in April's Department of Transportation ranking. It rose to 7th in May.American Airlines, which has many bases with Spirit, also cancelled 454 flights, representing just 15% of its Monday schedule. Additional 674 flights, representing 22% of the schedule, were also delayed.American's Southernmost Hub, Miami International Airport, currently has 10 canceled and 118 delayed flights. For both American and Spirit, South Florida is the gateway to South America.CNBC reviewed a list and found that American had cancelled at least 30 flights because of a shortage in flight crews.Analysts projected Spirit as one of the first to recover from the COVID-19 epidemic because it focuses on leisure travel. Its aircraft were one of the first to be taken from temporary storage units in the American Southwest.A Deutsche Bank analyst states that Spirit Airlines' low-cost model places it in the ideal spot to win the pandemic.Since the beginning of last year's rebound in air travel, airlines have faced staff shortages. To stop the spread of the pandemic, airlines have parted ways with pilots and planes. Some are already feeling the effects from "over-scheduling" this season.American Airlines began a busy summer travel season in June with hundreds of cancellations. Southwest Airlines experienced a similar situation and later admitted that it had also had operational problems.In a second quarter earnings statement, Gary Kelly, chief executive officer of Southwest Airlines, stated that while the June surge in travel demand gave stability to our financial situation, it had a negative impact on our operations after a period of low demand caused by the pandemic. We are focusing on improving our operations to restore the network that meets demand.United Airlines claims that it avoided these issues by reaching an agreement with its pilot union in order to keep pilots ready and trained to fly.American did not immediately respond to Insider's request to comment.Business Insider has the original article.