Ryanair and Aer Lingus are set to raise their checked baggage fees by up to €15 for the busy summer holiday period.
Both airlines' 15kg checked bag fees increase from €15 to €25 per sector from June 1 to September 30.
A 20kg bag rises from €25 to €35 during the same period, and from €35 to €45 in the case of select, longer flights - to Corfu and the Canary Islands, for example.
"Our optional fees rise at peak times to reflect the higher costs of operations during peak times," said Robin Kiely, Ryanair's Head of Communications.
"Just 20pc of our customers check in a bag, and as part of our Always Getting Better programme, we have reduced our checked bag fees and increased our cabin baggage allocation, allowing customers to bring two free bags onboard," he added.
Summer months are among the busiest for Irish airports, with Dublin alone expecting some 330,000 passengers over the June bank holiday period.
The fee rises apply to all flights from June 1 to September, regardless of when they are booked.
Ryanair and Aer Lingus have implemented such rises in peak months for several years, and both plan to hike their fees over the Christmas holiday period too.
In addition, Ryanair's flight change fee rises from €30 to €40 on June 1 (or from €45 to €60 if paid at the airport or through its call centre). On Canary Island flights, the fee rises from €50 to €60 (or €75 to €90).
Aer Lingus's flight change fee remain the same at €40.
"Irish travellers benefit from some of the most competitive air fares across Europe," a spokesperson for Aer Lingus told Independent Travel.
"On short haul we are focused on providing the lowest priced seat and thereafter customers may choose from a menu of additional extras.
"We also offer customers a number of fare options including flexi fares whereby checked baggage is included in the fare package."
Aer Lingus maintains that its baggage fees are "competitive" when compared with other European low-cost carriers.
"We also operate a generous luggage allowance policy on long-haul flights."
In the past, families have been frustrated by higher baggage fees during school holiday periods. In contrast to scheduled flights, moreover, holiday charters often include a 20kg checked baggage allowance in the package price.
Ryanair and Aer Lingus both point out that their baggage and flight change fees are optional, and that passengers may carry an extra small item, such as a handbag or laptop, in addition to their regular 10kg carry-on allowance.
"Families travelling this summer on Ryanair's Family Extra service can also avail of half price checked-in bags for children," Kiely added.