The findings by Zack Polanski come as the airport's bid to expand is set to come before the Planning Inspectorate in December.
London City Airport says the proposal could boost the economy by more than £700m, and says planes to and from the airport in the first six months of the year were 70 per cent full on average.
Between January and June, 12,216 flights leave the international airport, situated in east London's Royal Docks.
But analysis of UK Civil Aviation Authority data by deputy Green Party leader Zack Polanski reveals 2,945 of these - equivalent to 16 a day, or 24.2 per cent of all departures - were more than half-empty.
In the first three months, just under one-third of all flights were at 50 per cent capacity or less.
London City Airport submitted plans in December 2022 to raise its annual passenger cap from 6.5 million to 9 million, introduce more morning flights, and allow flights on Saturday afternoons.
Its bid was unanimously refused by local authority Newham Council in July amid backlash from local residents, councils and MPs.
But the following month the airport submitted an appeal against this decision to the Planning Inspectorate. A two-week planning inquiry is now due to begin on December 5.
Mr Polanski, a Green Party London Assembly Member who has long opposed London City Airport on the grounds of pollution and noise concerns, blasted the airport's plan to expand.
“The audacity of London City Airport to push for expansion when they are not even close to filling their current flights is mystifying," he said.
"In the middle of a climate emergency, the last thing we should be doing is expanding half empty airports.
“This new data shows exactly how London City’s business model welcomes – if not relies on – half empty flights as long as they run more frequently, with no regard for the carbon they spew into the atmosphere or the likelihood of economic failure.
“Whoever the final decision falls to – the council, the Mayor, the Government – must block this profiteering for the sake of Londoners and the environment."
The Green Party compared the figures for London City Airport to the figures for Heathrow, which fared better with 17 per cent of flights half-full or less in the first quarter, and eight per cent in the second.
A London City Airport spokesperson responded: “Planes to and from London City in the first six months of this year were on average 70 per cent full, which is standard for our airlines.
“Seventy-five per cent of planes departing from London City during this period were almost 80 per cent full – higher than pre-pandemic levels.
“Our proposals seek to increase the current passenger limit to accommodate future growth over the next 10 years, without any increase in the number of permitted annual flights.
“If approved, our proposals could create 4,500 additional jobs across London and an additional £702m in Gross Value Added to London’s economy.”