15th April plus 28 days is Friday 13th May. Where do they get 9th May from?
They displayed their continuing lack of competence by getting the dates wrong.
The truth is
STATEMENT BY UNITE
May 4th, 2011 by admin
The following statement has been issued today (Wednesday) by Unite’s General Secretary Len McCluskey:
“There has been some clarity sought as to the last date on which Unite could give notice of industrial action pursuant to the last ballot it held of cabin crew members employed at British Airways. The company and the union confirm that notice of action may be given at any time up to midnight on May 15th.
“British Airways and Unite intend to make full use of the time available by continuing discussions aimed at securing a settlement to the dispute.”