• The foreign secretary said it would "establish the principle" and break people traffickers' business models.
• Seven or eight people are due to be removed on Tuesday, after dozens won legal cases to be taken off. But more legal challenges are set to be heard.
The first flight taking asylum seekers to Rwanda will take off and people who are not removed on Tuesday will be on subsequent flights, Liz Truss has said.
The foreign secretary said it would "establish the principle" and break people traffickers' business models.
Seven or eight people are due to be removed on Tuesday, after dozens won legal cases to be taken off. But more legal challenges are set to be heard.
Church of England leaders described the plan as an "immoral policy".
Three more legal challenges from people set to be flown to the east African nation's capital Kigali are expected to be heard in the courts before the flight departs.
A last-ditch attempt to block the flight altogether was rejected by the Court of Appeal on Monday, however.
Speaking to BBC Breakfast, Ms Truss confirmed the flight will depart as scheduled even if only a small number of people were on board, describing it as a "key part of our strategy for tacking the appalling people smugglers who are trading in people's hopes and dreams".
She said: "If people aren't on the flight today, they will be on subsequent flights to Rwanda.
Ms Truss added the government was prepared to "face down" future legal challenges to its plans, adding: "It's about making sure that people have a safe future in Rwanda and we're determined to follow through on it".
The flight on Tuesday evening was originally due to carry dozens of passengers, but most succeeded in their individual appeals against deportation.
It was not clear exactly how many will leave on the flight: on Monday night, the Home Office said it was eight, while the charity Care4Calais said the number had fallen to seven.
In a letter to the Times, senior Church of England leaders described the plan as an "immoral policy that shames Britain".
Signed by the archbishops of Canterbury and York and more than 20 other bishops who sit in the house of Lords, the letter said those being deported have had "no consideration of their asylum claim... or any attempt to understand their predicament".
Tuesday's flight is due to be the first in a five-year trial, in which some asylum seekers deemed to have entered the UK illegally are transported to Rwanda to claim refuge there.
They will get accommodation and support while the Rwandan government considers their application, and if they are successful they can stay in the country with up to five years' access to education and support.
If their asylum claim is unsuccessful, they will be offered the chance to apply for other immigration routes, but could face deportation from Rwanda.
The letter, signed by the entire senior leadership of the Church of England, said those being sent to Rwanda have had no chance to reunite with family in Britain.
"Many are desperate people fleeing unspeakable horrors. These are people Jesus had in mind as he said when we offer hospitality to a stranger, we do it for him," it says.
"We cannot offer asylum to everyone, but we must not outsource our ethical responsibilities, or discard international law - which protects the right to claim asylum."
Image: BBC
It's not the first time the Archbishop of Canterbury has criticised the plan - he described it as "the opposite of the nature of God" in his Easter sermon.
At the time, the Home Office responded that the UK had a "proud history" of supporting those in need.
The BBC has contacted the Home Office for a response to the letter.
On Monday, appeal court judges ruled the first deportation flight could go ahead, agreeing with a previous judgement that it was in the "public interest" for the government to carry out its policies.
Campaigners had hoped to stop the plane taking off before a full hearing on whether the policy is lawful next month.
Speaking in the Commons on Monday, Labour's shadow home secretary Yvette Cooper described the plan as "profoundly un-British".
But Rwanda's high commissioner Johnston Busingye earlier defended the partnership, telling the Daily Telegraph people arriving in the country would be treated with "safety, dignity and respect".