TORONTO -- Porter Airlines will begin charging $25 for the first bag and $35 for a second bag checked on travel booked after April 21.

The Toronto-based airline said Friday that previous rules will continue to apply for flights booked before April 21 or for travel occurring before May 14.

Porter's spokesman says the airline is trying to strike a balance between allowing passengers to carry more baggage under a higher weight allowance brought in last year and its need to compete with airlines that charge a wider range of fees.

"Airfares are very competitive and passengers are benefiting from lower prices by as much as 60 per cent where Porter provides competition," Porter spokesman Brad Cicero said in an email.