Rishi Sunak’s government is considering concessions on the Rwanda deportation bill to allow exemptions for Afghans who served alongside UK forces, parliamentary sources say. Ministers are also being pressed to give ground to an amendment to the legislation so that the east African country could be ruled unsafe by a monitoring committee. This comes after peers blocked the flagship bill for a third time on Tuesday night by backing four amendments. Sunak is under pressure from his own MPs to ensure that planes take off this spring, in the hope they can revive the Conservative party’s political fortunes. The Rwanda (asylum and immigration) bill will return to the Commons at Wednesday lunchtime and is expected to move to the Lords hours later. The amendment enacting the Afghan exemption, put forward by Des Browne, a former Labour defence secretary, secured the biggest majority – of 57 – with peers backing it by 275 votes to 218. A Tory source said the government was considering “options” on an Afghan exemption. The Lords also agreed to a measure by the crossbench peer David Hope requiring Rwanda to pass an independent verification before it was considered safe. The amendment by Lord Hope, a former head of the Scottish judiciary, has significant support within the Lords, especially among crossbenchers. It is understood that he is expected to table a narrower amendment, which could gain more support across the Lords. Ministers have so far resisted offering any concessions apart from a minor proposal for an annual report on the impact of the bill on victims of modern slavery and trafficking. Parliamentary ping-pong between the Commons and the Lords could continue late into Wednesday night. If the matter is not settled, the bill is expected to return to parliament on Monday. It emerged on Tuesday that AirTanker, an aviation company that provides a fleet of 14 airbuses to the RAF to fuel and transport the military, is being lined up to take asylum seekers to Rwanda, which could plug a big gap in the government’s plans. AirTanker, whose involvement in talks over the Rwanda plan was revealed by the Guardian, declined to comment. Sunak would not comment on reports that RAF aircraft could be used to deport asylum seekers. Asked whether it would be appropriate to use RAF aircraft, he told broadcasters: “My priority is to stop the boats. I said this very clearly when I became prime minister, and right now we are trying to get the bill through parliament in the face of enormous opposition from the Labour party.” He added: “We must stop the boats because it is a matter of fairness.” The bill, and its allied new treaty with Rwanda, aims to answer supreme court criticism that the African state is unsafe for people deported from the UK. Officials say flights for Kigali will not take off for several weeks. Sunak has made “stopping the boats” a key pledge of his leadership before the general electooin. Boris Johnson announced two years ago that “tens of thousands” of asylum seekers would be sent to Rwanda within weeks but so far, no one has been sent. The scheme will cost £541m if 300 asylum seekers are sent to east Africa, the government’s official auditors have concluded.