The pilot due to fly a 'Moyes Out' banner over Old Trafford on Saturday said he would also carry a banner in support of the manager if he was asked to.
Speaking to ITV News sports correspondent Ian Payne, Chris Mustow said his company Air Ads had declined some "colourful" requests for messages in the past.
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The four artworks shortlisted for this year's Turner Prize include a huge golden sculpture of buttocks, and more than £20,000 in pennies.
A proposal to sell ivory stockpiles and return profits to communities that sustain elephants has been defeated at a major global conference.