More helicopters are urgently needed to deliver aid to the millions of Pakistanis still cut off by devastating floods, says the UN's food agency.
Many roads have been blocked and bridges washed away by what UN head Ban Ki-moon called a "slow-motion tsunami".
Millions of people need food, shelter and water after weeks of floods that have submerged much of the country.
Aid agencies have said funding for relief operations is increasing but much more is needed.
The monsoon-triggered floods have affected about one-fifth of Pakistan.
About 1,600 people have been killed and an estimated 20 million people affected by the worst floods in Pakistan's history.
Tens of thousands of villages remain underwater and there are warnings the crisis may worsen as flood waters continue to surge south along the Indus River.
Experts have warned that greater relief efforts are needed to avoid a second wave of deaths from water-borne diseases such as cholera.
Spokeswoman for the UN's World Food Programme (WFP), Emilia Casella, said the agency only had 10 helicopters at its disposal but expected to have another five later on Friday.
She said it was not enough: "If you do the math, we are trying to reach six million people and today we've reached 1.2 million."
"You need to have helicopters in rotation numerous times a day to communities to get the capacity up. We need the helicopters now... but the helicopters have to be funded," she said in Geneva.
Many more helicopters could be brought in and the WFP would make use of them all, Ms Casella said, highlighting the extent of the need.
A WFP official in Pakistan's capital, Islamabad, said the agency was currently using Pakistani and US army helicopters.
The Pakistani military had 45 helicopters involved in relief operations and 60,000 troops while the US military had 15 helicopters helping, Pakistani army spokesman Gen Athar Abbas told the BBC.
Donors pledged more money for Pakistan at a special session of the UN General Assembly on Thursday after concerns that the international community was not acting with the urgency the situation demands.
Pakistani Foreign Minister Shah Mahmood Qureshi said he had been assured that the UN's target of $460m (£295m) would be "easily met".
On Friday, the UN said 55% of the target had been met but that the appeal would be raised in the coming weeks to try to meet the immense needs that were becoming clear.
"It's a disaster that came very slowly," said Elisabeth Byrs, spokeswoman for the UN Office for the Co-ordination of Humanitarian Affairs.
"It's not an earthquake that hits suddenly that we can immediately see the victims. But we are now seeing the magnitude of this catastrophe."
At the UN session on Thursday, Ban Ki-moon said the floods were like a "slow-motion tsunami" that posed "one of the greatest tests of global solidarity".
A number of countries have now announced further contributions for Pakistan.
The US - already the biggest donor - announced it would contribute another $60m, bringing its total to more than $150m.
Secretary of State Hillary Clinton said about $92m would go to the UN's appeal.
The EU has also increased its pledge to more than $180m and the UK is nearly doubling its contribution to almost $100m.
Germany has raised its aid to $32m and Mr Qureshi said Saudi Arabia was pledging more than $100m.
Analysts have said it will take many billions of dollars for Pakistan to recover from the damage wrought by the unprecedented flooding.
If you would like to make a donation to help people affected by the floods in Pakistan, you can do so through the UK's Disasters Emergency Committee at www.dec.org.uk or by telephone on 0370 60 60 900.