From Amex:
Purchase a round-trip Upper Class ticket on Virgin Atlantic between the US and London and receive a free economy round-trip ticket to London. Must register with the Virgin Flying Club before you fly and travel 1/1/00-5/31/00. To register, call 1-800-365-9500 and mention code AX2F.

Sorry if this is a repeat!

AMEX had a great promotion way back when if you flew Upper Class.

You always get enough points for a free economy ticket to London your first time flying Upper Class, though.

My impression was that this promotion would allow you to gain an extra economy ticket. It is worded: "If this is your first Upper Class flight on Virgin, you'll also receive enough bonus miles for an ADDITIONAL free economy ticket." The small print reads: "Free ticket will appear as a free ticket on your next Flying Club account statement. Free ticket must be redeemed by 12/31/00. Upper Class passengers earn double miles. ADDITIONALLY, first-time Upper Class passengers will earn enough for an ADDITIONAL Economy class ticket between the US and London. These miles will also appear on your next statement."