In an open letter to US President Barack Obama, four former air force officials have called for a rethink on the drone programme, which has claimed many innocent lives and serves terrorists by fuelling hatred against America. The former officials, who have operated drones in conflict zones, said that targeted killings by unmanned aircraft had become a major driving force for terror outfits.

"We cannot sit silently by and witness tragedies like the attacks in Paris, knowing the devastating effects the drone program has overseas and at home," they wrote in the letter, which comes in the backdrop of Obama clarifying that US troops will not be sent in large numbers to Syria.

However, such a strategy would imply a stronger reliance on aerial attacks with more drones being used to eliminate terrorists. Drones have been used in combat operations in Afghanistan and Iraq, and in counter-terrorism efforts in Pakistan, Yemen, and Somalia.

In his first two years at office, the US president had authorised nearly four times the number of drone strikes in Pakistan, in comparison to what president Bush had did in eight years, a New America Foundation study has claimed. Drone strikes are being favoured as fewer American armed personnel are harmed on ground, and it is a low-cost alternative to deploying conventional forces.

Aimed primarily at al-Qaeda and the Taliban, the airstrikes, often result in civilian deaths due to mistaken targeting. The numbers reported vary between thousands, as cited by local sources, while the US administration claims that a few handful of civilians are killed in drone strikes. Up to 90% of those killed in drone strikes are unintended targets, according to The Intercept, while the Pentagon has plans to increase daily drone flights by 50% until 2019.

The four whistle-blowers include Brandon Bryant, 30, and Michael Haas, 29, who have served in the 15th Reconnaissance Squadron and 3rd Special Operations Squadron from 2005 to 2011; Stephen Lewis, 29, who was with the 3rd Special Operations Squadron between 2005 and 2010 and Cian Westmoreland, 28, a technician who served with the 606 Air Control Squadron in Germany and the 73rd Expeditionary Air Control Squadron in Kandahar, Afghanistan.

They are represented legally by Jesselyn Radack, director of national security and human rights at the nonprofit ExposeFacts.

Bryant, who was part of the team that tracked and killed al-Qaeda leader Anwar al-Awlaki told the Guardian, "We just understand that in its current form the program is being abused, there's no transparency, and we need to be open to other solutions."

Referring to al-Awlaki's killing, he pointed out that article 3 of section 2 of the US constitution states "even a traitor deserves a fair trial in front of a jury of his peers".