The rules are changing in the fall and per the WSJ there is confusion at the moment. Here is their take for thu summer:
*What are airline refund rules this summer?
The most important thing to know: Airlines are already required to issue a refund if they cancel or significantly delay your flight, even if weather is to blame. This applies whether you travel first class or bought a restrictive basic economy ticket. (The definition of significant delay varies by airline, something the new rules will fix.
They might not volunteer that information, preferring to rebook you on the next available flight or issue a travel credit if you decide not to fly. If you don’t want either, ask for a refund to your credit card.
Of course, many of us need to get to our destination, making rebooking the only viable option unless you have a pile of cash or loyalty points. Last-minute flights are pricey, so refunds often won’t cover the cost of switching to another airline. Some airlines will put you on a competitor’s flight at their expense if the troubles are their fault, but that’s generally not their first choice. It never hurts to ask.*