Coach seating

Hi Frank,

What you seat on will be,  un siège,  as the chair you sit on where rows of them have been placed for that purpose in a cinema, a plane or a bus.

But if you talk of a 50- seat coach you will use 'place' as this link illustrates -

https://www.groupito.com/articles/combien-de-places-dans-un-bus

Hope this helps!

For planes? ( In many places, coach refers to a tour bus, not economy class on planes). 

Siège/s (d’avion) en classe économique, although anglicismes are rife in this terminology now !