British Airways: Upgrade to First

From the UK:

Our current offer of a fully flexible one-way Upgrade to First is valid until 27 May, but our semi-flexible offer which was open for a limited period only, is now closed for booking. So if you’ve already bought your Upgrade to First return ticket as part of the semi-flexible offer you still have until 27 May to travel.

From the UAE / Oman / Saudi Arabia / Kuwait / Bahrain / Qatar (travel through 31 May, outbound):

Now through 31 May 2011 you can take advantage of a special 15%* reduced fare and upgrade one leg of your journey to First.  You will soon discover that a long flight, becomes not long enough, when you travel in our award winning Club World and First cabins.