Simon Calder: A mean Spirit in the skies for budget flyers?

Of all the year's flights, those in the eighth month are the most cherished, since they usually whisk us away to distant shores where barbecue summers are the norm, together with long, warm August nights. As it happens, they are the ones the airlines adore, too, since the peak holiday month is more profitable than any other.

This summer, a couple of airlines are aiming to make even more cash than usual. Ryanair this week announced that the fee for checking in a bag during July and August will rise from £15 to £20 each way – representing an increase for a family of four flying to the Med and back, each with a checked-in bag, from £120 to £160. The airline says it aims "to incentivise passengers to travel light this summer", and that seven out of 10 "Ryanair passengers will be unaffected by these changes because they travel with no checked-in bags". But that is a system-wide, year-long average: in summer, when the ratio of holiday to business travellers increases, more passengers tend to check in bags.

What Ryanair does is highly significant, since it carries more passengers than the newly merged British Airways and Iberia (and enjoys a higher market capitalisation, too). When the Irish airline first introduced baggage charges, they were intended to be "revenue-neutral" – but now they contribute to Ryanair's very healthy profits. The current forecast puts the carrier on course to make a margin of around £4 for every seat filled this year. (For comparison, easyJet made around £1 a head in its last financial year, while BA lost £13 for each customer flown.)

Every Ryanair passenger is allowed to take a bag on board, and pop it into the overhead locker. But a low-cost carrier in the US is now charging even for that small courtesy. For flights from 1 August, Spirit Airlines charges up to $45 (£30) for cabin baggage.

Who is Spirit? "Arguably the best airline in the Americas", at least according to its own publicity. For possessors of the pathetic pound, Spirit has plenty of appeal. It has a useful network of cheap flights from its Florida hub (which it ambitiously calls "Fort Lauderdale-Miami) to a range of Latin American cities: if today's Traveller's Guide to Nicaragua (starting on page18) inspires you, save a small fortune by buying a cheap flight to Miami (around £450), catching the train to Fort Lauderdale and stepping aboard a Spirit Airbus for the $172 (£114) round-trip to Managua's dismal airport. And, until 31 July, you can carry aboard a spectacularly large piece of hand luggage with a volume of 77 litres. But starting in August, the capacity falls to 65 litres and charges begin.

Will you soon need to show up only in the clothes you stand up in to avoid charges? Not quite: Spirit passengers are allowed a "personal item" that fits under the seat in front of you – though on the long haul to Lima, you may start longing for some more legroom. In addition, you can take a camera, umbrella, coat, hat, book and food: good luck lugging all of those on board.

Many more British travellers fly to Málaga than to Managua. For most of us, the crucial question is: could it happen here? From "Speedy Boarding" to extra legroom, airlines serving the UK are normally far ahead in concocting new ways to add charges. Tim Jeans, managing director of Monarch, says a carry-on fee would be a step too far – but he believes that current cabin-baggage rules must be more rigorously enforced.

"This fee is more to do with passenger convenience than making money," he says. "Too many flights are delayed because there is too much hand baggage."

Michael O'Leary, chief executive of Ryanair, says "The Spirit Airlines announcement strikes me as a recipe for delays at the boarding gate, which we would not tolerate". And those peak summer price rises for checked-in baggage on his airline?

"The more passengers travel with carry-on luggage and the less they check-in bags, the more we will like it and the lower our fares will be."

Luck runs out for visitors to Vegas

A ticket on Spirit Airlines is one of many purchases in America that could end up costing more than you expected – even in Las Vegas. In the past decade, Virgin Atlantic has carried two million Brits from Gatwick to Nevada's largest city. For years, Las Vegas was the cheapskate's favourite US bolthole: gambling earnings helped to subsidise everything from breakfast to ballet. With a location amid some of America's most dramatic landscapes, and unrivalled entertainment, Vegas offered low prices and high excitement. Indeed, Virgin's latest route will link Manchester with Las Vegas. But the slump in sterling – and in visitor numbers – has taken off the city's shine.

Malcolm Howitt says his daughter and her family have just returned from a trip to the desert city where they found "everything, especially food has become prohibitively expensive. Taxi drivers routinely take a circuitous route from the airport, replying to their passengers' remonstrations that they have to make a living, there being a surfeit of taxis".

Tipping is mandatory. Give bartenders $1 per drink, says the US advice website, tip20.com. Even your tattooist needs 20 per cent, or "more for custom or difficult work". But it concedes you need not tip a concierge when asking for directions.