The nearest airport to Benidorm is Alicante Airport, which is around 40 minutes away by car. There are also regular flights from all over the UK and Europe, so it's easy to get to Benidorm from most major airports.
If you're looking for cheap Benidorm holidays, it's worth checking out budget airlines, as they often have sales on flights — so you could save a lot of money on your holiday if you book in advance.