"If a balloon flying over London makes people laugh, I think that's absolutely worth it", she says.
Trump and Melania landed on Air Force One at 2pm to begin their four-day tour of the UK in London, reports Metro UK.
Protesters were expected to rally during his visit.
On Friday evening, Trump and the First Lady whisk up to Scotland for a weekend of golf and relaxation - and more protests outside his resort.
Unlike visits from previous presidents, he won't be spending much time in London after his arrival.
"And me mate said "If you call it the Trump Arms I'll organise the party". "It seems so un-American".
Johnson has told reporters that Americans respected peaceful protest.
"Boris Johnson's a friend of mine, he's been very nice to me, very supportive and maybe I'll speak to him when I get over there".
Trump will travel by helicopter once there, making it unlikely he'll see protests firsthand.
Mr. Trump angered May and many Britons by tweeting inflammatory and unverified videos made by Britain First, an anti-Muslim group whose leaders have been convicted of hate crimes, and by characterizing parts of London and other cities as no-go areas because of a purported Muslim-related crime wave. Both of those accords were the result of years of painstaking diplomacy by European leaders - and Trump unilaterally trashed them.
During his news conference on Thursday, the USA president also appeared to refer to Ireland as part of the United Kingdom.
Mr Morgan, the forthright journalist and broadcaster, hit back and questioned why the London mayor had not been so vocal over the visit of controversial Turkish President Recep Erdogan. That prompted almost half a million people to sign a petition calling for Trump to be banned from the UK.
Mr Trump's son, Eric, arrived in Aberdeen earlier on Thursday to play at the nearby Menie golf course, which is also owned by the family. It was an extraordinary rebuke from a close ally.
Fresh from a North Atlantic Treaty Organisation summit where Trump chided Germany and other European nations for failing to contribute enough to defence spending, British Prime Minister Theresa May is hoping his trip will boost the close ties between their two nations and help forge a future free trade deal.
Mr Trump will meet the US Ambassador at Winfield House after arriving and then head to Blenheim Palace in Oxfordshire.
Mr Khan defended the blimp baby: "There are two issues; one is the freedom to protest and the right to free speech and the second is our issues on President Trump".
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