Is a request to book a business flight ticket for a graduate student an unreasonable one? As a Ph.D. student from a (pretty rich!) European research group, I'm about to attend a conference in New Zealand. The second leg of a potential flight takes 16 hours to reach the destination, and it seems to be the hell of discomfort to spend all that time on an economy seat (I once had a 10-hour-flight experience, and I was in trouble because of my relatively long legs despite time-to-time walks in the plane's aisle). The cost of a business seat is around 4 times the cost of an economy one, something around 3500 Euros. Thus, I'm just wondering how reasonable the request to have such a seat is. 

PS. I do know that a first-hand approach is actually asking my supervisor what he thinks about it. But I'd rather not ask such a question if it would sound silly and unreasonable. 

Any experiences and thoughts (particularly from those who had already been involved in any side of such a situation) are welcome!
In Canada it is illegal to get anything but economy fare (including trains) and charge this to any one of the national tri-Council grants (there are exceptions if there is no other availability but this is rarely the case.)

The best you can do is buy an upgradable economy fare and hope for the best, or pay for an exit-row seat.

Overall your request will be perceived not only unreasonable but also blatantly unreasonable, unless you have special conditions or a rich sponsor.

I can say more.  Some years ago a candidate for a position where I work insisted on getting a business-class ticket for the interview and he was just removed from the shortlist.  

Edit: is this a direct flight?  This wiki list of long flights https://en.m.wikipedia.org/wiki/Longest_flights does not include European-Asian city pairs.