Join Date: Oct 2006
Location: London, UK
Programs: BA Gold, VS Silver, SQ Silver, IHG Plat Amb, Hilton Gold, Marriott Plat, Accor Silver, Radisson Prem
Posts: 16,873
No, either swap for the whole flight or not at all.
The F passenger can invite another passenger for drinks at crew discretion but not for the meal service.
Many travel F for the privacy, and swapping mid-flight would not be appreciated.