facetime error while international

[Ris81]

I have an iphone4 and was recently out of the country. I was in airplane mode and had my wifi on the whole time. My husband, who has an iTouch, was still in the USA. If facetime requires wifi, how come I was unable to facetime with my husband? (It works when we're both in the US). He plans to get an iphone soon, will that solve the problem? Thanks in advance for your help!!

 

[Ris81]

I should also add that my sister-in-law had brought her iPad2 that uses only wifi and I had no problems using facetime with my husband using her iPad. thanks.