Gate card: Aer Lingus (EI)

The airline's policy: “None (no named customer-of-size policy); extra seats sold under 'Purchasing an extra seat'”

Aer Lingus has no formal customer-of-size policy page. Its Seats Information page simply says you can purchase an extra seat for comfort, online or by phone, paying the relevant fare plus taxes/charges/admin fees. Important caveat: on transatlantic flights, Economy armrests do not fully retract into the seat-back, so an extra economy seat may not let you use the combined width of both seats; Business Class armrests are fully retractable.

Refunds: Not explicitly published for extra seats. The page's seat-fee rule states seat fees are non-refundable, except that if the purchased seat (or an equivalent seat sold at the same price) is unavailable on the day of travel, a full refund can be claimed via the Extras Refund Request Form - that wording targets seat-selection fees rather than the extra-seat fare.