Like most, the airline industry has been rocked by the COVID-19 pandemic. However, some airlines have navigated today's rough waters better than others. Personal finance company NerdWallet recently examined some of the top U.S. airlines' responses to the coronavirus crisis, looking at booking flexibility, health and safety measures implemented and other actions taken that have either enhanced or hindered the customer experience to determine which have handled the ongoing crisis the best thus far.

Alaska Airlines, which recently began handing out yellow cards to passengers who refuse to wear a mask, earns an A for health and safety and a B+ for flexibility for an overall grade of A. Last month, the airline expanded its Next-Level Care safety measures, which include a required health agreement during check-in.

American Airlines has been one of the biggest losers during the pandemic, earning a grade of D overall, including an F for health and safety. NerdWallet knocked the carrier for its poor conveying of policy changes in the wake of global lockdowns as well as the fact that it didn't allow online itinerary changes for several months.

Despite a rough second quarter, Delta Air Lines continues to set an excellent example, earning an A for its response to the COVID-19 crisis. NerdWallet commended the airline for its clear, customer-first information and policies. Delta also continues to limit capacity on its flights and received an A for health and safety.

Hawaiian Airlines has been severely impacted by the coronavirus pandemic as Hawaii remains virtually off-limits to travelers amid tight restrictions. To this point, the airline has earned a C+ for its handling of these unprecedented times, including a B- for flexibility.

Despite strong face-covering enforcement, JetBlue only earns a C from NerdWallet for health and safety. Still, the airline's overall B- ranks fourth-best among the seven airlines that were analyzed this summer.

One of the carriers blocking seats to allow for physical distancing through the summer, Southwest has navigated the COVID-19 crisis as well as could be expected, earning an A from NerdWallet, which noted the low-cost carrier "ran fare sales while other airlines were keeping prices high."

Another carrier not blocking seats this summer, United Airlines received a C- for its handling of the coronavirus pandemic. The airline was knocked for its confusing voucher policy and a devalued mileage program, according to NerdWallet.