Map view on Google Flights is probably the best option for this. It's kind of slow and wonky and probably has some stale data, but I haven't seen anything bett

Map view on Google Flights is probably the best option for this. It's kind of slow and wonky and probably has some stale data, but I haven't seen anything better. In principle, yes you can build this. In practice, no air provider/aggregator wants you to be running that many low conversion searches across their inventory. So you can try to (very slowly) aggregate results yourself across a wide variety of free services to cover a sufficient number of airlines+destinations, or sign some paid deal with an aggregator to do it for you, and then probably still have to run a bunch of distinct searches for every destination you want to cover. This isn't particularly economical to provide as a service.