Papua New Guinea's Salvation Army says investing half a billion US dollars into airport development is too much for a country that struggles to feed its citizens.
The Jackson International Airport in Port Moresby is set to be upgraded to allow an increase in passengers and aircraft traffic.
The expansion follows pressure from the huge liquefied gas project.
The group's spokesperson, John Kerari, says the money should be spent to benefit all people in PNG, not just a few.
"It's sad that we talk about this development that will benefit only a few handful of people while a majority of our citizens would rather see some improvement in education, clean water, health services and that sort of thing."
But the National Airport Corporation managing director, Joseph Kintau, says the investment is set to come from a number of sources, including private investors.