Hi Linzi. In my experience all Airlines seem to have different rules for this kind of thing. Some have limits based on age and others on weight or some based on both age and weight. . I think BA have a limit of 2 years, but as I said earlier, you reallyl need to check with your chosen airline. Virgin I think was 12 mnths last time we flew. Hope this helps Have a great holiday! Airlines really should put some effort into making these things clearer for parents!!