Trump was expected to head first to the presidential compound of Turkish leader Recep Tayyip Erdogan, a close ally who is hosting the 2026 gathering.
Just before Air Force One touched down in Ankara on Tuesday, NATO showcased a series of military projects worth billions of dollars - an investment that the alliance's secretary-general, Mark Rutte, called "money well spent".
An energised Rutte was speaking to government ministers and defence industry officials at a forum billed as NATO's "big reveal", to the thrum of techno music and a slick video display.
NATO as an organisation does not own any weapons - these are the property of the 32 member countries - but it does have a fleet of 14 AWACS early-warning radar surveillance planes that are about 50 years old, along with some newer surveillance drones.
A deal to replace the ageing planes was announced on Tuesday.
Swedish manufacturer Saab will be supplying up to 10 new GlobalEye surveillance aircraft for a 10-nation consortium, Swedish Prime Minister Ulf Kristersson announced.
"It's a moment of great pride," he said, noting that the twin-engine aircraft would be "made within the alliance for all the alliance".
"We need to ensure that we are translating our economic might into military capabilities, putting the cash to work from defence plans to drones, from money to missiles and interceptors," Rutte said.
Trump has branded NATO a "paper tiger" that would cease to function without American arms and leadership.
At the forum on Tuesday, Michael Duffy, a US undersecretary of defence, said "the reality is that we need production increases across the board".
"We will be looking to increase our exports to those who are looking to buy our equipment, and we'll also be looking to partner with the expansion of production capacity here in Europe," he said.
Representatives from 15 nations shook hands and patted shoulders on a vast podium under the NATO logo as they announced a multinational effort to buy air-to-air refuelling and transport planes from Airbus.
Then Rutte announced a four-country effort to purchase as many as five new Triton surveillance drones to add to NATO's small fleet.
Rutte told reporters on the eve of the military alliance's two-day summit in Turkey that "we will announce tens of billions in new contracts that will provide the crucial kit we need to deter and defend".
However, at Tuesday's event, no dollar figures were given and the display included some projects long since agreed.
The defence industry splash comes a few weeks after Rutte tried to ease US concerns about military spending at NATO with a new pitch using a chart labelled "The Trump Trillion" - showing $A1.2 trillion ($A1.7 trillion) in spending by European allies and Canada since 2017.
Far from being impressed, Trump appeared unmoved, saying he was still disappointed at some NATO allies' refusal to join the Iran war, which he had launched alongside Israel without consulting them.
"We don't need their money - we don't need anything," Trump said.
"I just want loyalty."
The summit is being held in Erdogan's sprawling palace compound in Ankara, with the focus a stronger Europe for a stronger NATO.
The Trump administration has warned the allies that they must handle Europe's security alone as the United States focuses on China and the Indo-Pacific region.
Concern is mounting among some northern and central eastern countries that Russia might be preparing a hybrid attack - a combination of conventional warfare with tactics like cyberattacks - on the continent as Russian President Vladimir Putin struggles to secure victory in Ukraine.
