Aer Lingus short haul passengers face baggage charges of €8 on each item of baggage from today.
However passengers will only have to pay half that if they check in online in advance.
Aer Lingus said the new charges will facilitate quick and easy access through airports and ensure quicker turnaround times.
Fares may also be reduced as a result.
Passengers will be allowed carry up to 20 kilos for €8.
They will be charged another €8 for each kilo over that threshold.
Passengers will still be allowed to carry hand luggage into the cabin as long it weighs less than six kilos.
Ryanair introduced check-in charges for baggage in March 2006.
