Boris Johnson said this week that he “probably needs” a plane to help him discharge the duties of Foreign Secretary.

Mr Johnson – along with the Prime Minister and other cabinet colleagues – already has access to the Royal Air Force’s Voyager jet, but he claims “it seems to be very difficult to get hold of.”

But would the so-called “JumBoJo Jet” be value for money?

How much does it cost to fly the Foreign Secretary?

We asked the Foreign Office for details of how much it costs to get Mr Johnson around the world. They’ve not got back to us, but we’ll update this article if they do.

In the meantime, let’s look at what data is available.

Foreign Office statistics show that Mr Johnson made over 50 international trips last year – around half of which used the services of the Royal Air Force, who then charge the Foreign Office for costs incurred. Mr Johnson used commercial airlines for all or part of his travel on some 16 trips in 2017.

We don’t have a complete account of the cost of all these trips. But we do know that the trips where Mr Johnson only used the services of the RAF cost the Foreign Office, on average, £4,266 each.

The stats also include information on how much was spent on Mr Johnson’s trip overall, including accommodation, meals and flights. So for instance, we know that £3,831 was spent on Mr Johnson’s short stay in New York in April last year. We don’t know how many officials accompanied him on that visit, but we can see from other excursions that he usually takes four or five staffers with him. On that basis, we estimate that the Foreign Office spent about £19,000 on the trip overall.

We’ve applied that methodology to the other gaps in the figures. Based on the data available, we estimate that last year, Mr Johnson’s department spent a total of £350,000 on his foreign trips.

How much would a private jet cost?

The question is, would a private jet be a better use of public money?

It’s not clear what type of plane Mr Johnson has in mind, but perhaps astutely, he pointed out that “the taxpayers won’t want us to have some luxurious new plane.”

So let’s not look at anything too fancy.

The very cheapest private plane available – the Cirrus Vision Jet – could be Mr Johnson’s for a mere $1.96 million (£1.5 million). Then you’ve got ongoing fuel, crew and maintenance costs, which come to $155,000 a year (about £120,000).

But as you might expect, it is dinky.

The cabin measures just 4.1 feet by 5.1 feet, and has room for five adult passengers. Its range is about 1,200 miles – fine for Europe, but probably not enough for visits further afield.

We’re not sure this would quite meet the Foreign Secretary’s needs.

So what about a slightly bigger model? The Learjet 75 seats nine passengers – enough for the Foreign Secretary and a small team.

According to private jet firm Liberty Jet, this particular model would set you back $7 million, or £5.25 million. And then you’ve got running costs, which for 400 hours’ flying time a year, would come to just under £900,000.

Over ten years, including purchase costs, even this relatively small plane would cost the taxpayer £14.2 million. And it only has a range of 2,040 nautical miles – so you’d probably need a pitstop to get from London to New York.

The Embraer Legacy 650E has a range of 3,900 nautical miles – just under 4,500 regular miles. It can seat 14 passengers, but it comes at a cost. Just over £7.1 million to be precise, plus ongoing costs of £1.4 million a year. Over a decade, this model would cost about £20.5 million.

FactCheck verdict

Boris Johnson has suggested that he might need his own plane because the RAF jet to which he has access is often in use.

From the best data available, we estimate the Foreign Office currently spends around £350,000 a year on Mr Johnson’s air travel.

The very cheapest private jet available would cost £1.5 million to buy. The annual running costs would be about £120,000. But it’s very small and wouldn’t have the range Mr Johnson needs to reach major destinations around the world.

We looked at two slightly larger jets. A nine-seater Learjet would cost £5.25 million to buy and just under £900,000 a year to maintain. A 14-seater Embraer Legacy plane comes in at £7.1 million to purchase, and costs £1.4 million a year to maintain.

Even the cost of maintaining one of these planes would be double or triple Mr Johnson’s current travel spending – never mind the cost of purchasing the jet. We can’t see how Boris Johnson could get his own plane as Foreign Secretary without greatly increasing the amount the taxpayer spends on his international travel.