An environmental group has praised Welsh government ministers for cutting flights they take, but criticised them for funding a north-south air link.
WWF said the assembly government had cut air travel by 42% since 2006 and gave it a "green" rating.
But it said the Anglesey-Cardiff flights were "completely unnecessary".
The assembly government said the air link "needs to be put into the context of the bigger transport picture".
WWF used Freedom of Information requests to examine the flights taken by 19 UK government deparments or bodies plus the three devolved UK administrations.
It found the assembly government cut its flights by 42% between 2006 and 2009, second only to the Department for Environment, Food and Rural Affairs.
The report, Excess Baggage: the case for reducing government flying, gave the assembly government a green rating for its commitment to reducing flights taken by ministers, AMs and civil servants.
It found that in the last financial year the most used domestic flight by assembly government ministers, AMs and civil servants was Cardiff-Edinburgh, 168 times.
The top short haul route was Bristol-Brussels in Belgium, taken 30 times and the top long haul route was London-Luanda in Angola, used four times.
But WWF said there were "still issues to be addressed" if assembly ministers were "serious about limiting their impact on the environment through reducing flying".
It said the group had "major concerns" about the twice-a-day air link between Cardiff and Anglesey which was backed by up to £2.4m from the assembly government over three years.
It said the flights undermined assembly government climate change targets and funding would be better spent on rail links.
The service had a two month break this year when the previous operator went into administration, but resumed last month when it was taken over by Isle of Man-based Manx2.
The service was dubbed "Ieuan Air" by Conservative AMs in 2008 when they revealed Deputy First Minister and Anglesey AM Ieuan Wyn Jones had used the service 42 times since its launch a year earlier.
WWF Cymru head Anne Meikle said: "WWF are of the opinion these flights are completely unnecessary and undermine the climate change and sustainability targets the Welsh Assembly Government themselves have set for Wales."
Friends of the Earth Cymru director Gordon James said: "If the assembly government aspires to be one of the greenest governments in the world, then it should not be subsidising this flight.
"It would be a sign of commitment to its climate change ambitions if the subsidy was invested in the north Wales rail link."
The Welsh Assembly Government said: "For the first time ever we now spend more on sustainable forms of transport than we do on more traditional areas like roads.
"As well as supporting the air link, we have improved north-south rail and road links and we are committed to further improving the reliability and speed of journeys between north and south."