CO will accept requests for, and can even "determine" necessary the exclusive use of two seats for one pax, subject to availability, of course.
From the Contract of Carriage:
RULE 6 TICKETS
I) Passengers Occupying Two Seats
Upon request, or if determined necessary by CO, and given availability, a Passenger will be permitted to the exclusive use of two seats subject to the payment of two applicable fares for the points between which the two seats will be used. A Ticket will be issued for each seat and the normal free baggage allowance will apply in connection with each such Ticket presented to CO.
But there ain't no guarantee that the two seats are gonna be next to one another:
RULE 4 RESERVATIONS — CONFIRMATION/FARE QUOTES/DISCLOSURES
H) CO does not guarantee allocation of any particular seat in the aircraft, including advanced seat requests.
Of course, the government could step in and require that the airlines provide a First Class seat to any passenger with a 55" or larger waist.
