not necessarily...
but you still can use a blank logo , by making your logo all white and then uploading it
You can do this through MS Paint.
1) Go to Start > Programs > Accessories > Paint
2) Go to Image > Attributes
3) When the box comes up, type in 300 in the first box and 90 in the second
4) After that,
LEAVE THE "BOX" BLANK 
5) Then, of course, save it as JPEG or PNG or GIF format. I prefer JPEG
6) Then upload it into Airline Mogul (I am SURE you know how to do that), by going to Admin page and clicking below of what's your old logo. (the blue here button)
Press choose and then select your saved file:
If it is successful, you will get the "success" message. if it isn't, double check the above ^ instructions. If it still doesn't solve it, PM me!
Hope this helps... I spend 1 hour typing this
