Check with El Nido resorts directly for your flight options as I am sure they will be able to help you as they were most helpful when I was inquiring about going over there. The flights are air charters by Island Transvoyager. We ended up with a trip to Coron instead due to budget constraints, but I definitely want to visit El Nido again!

Mid-March onwards is probably the start of the summer vacation there so it be best if you start firming up your plans soon.