The Vote Now Show, the daily dose of The Now Show on Radio 4, has improved since the beginning of the election campaign. I like the mini-sketches by contributors. On Wednesday, John Finnemore offered some lovely gags in his "manifestos for smaller parties" skit. The jokes got groanier and groanier until we got to the party that wanted "improved facilities for overweight train-spotters". "They're standing on a broad platform." No? Suit yourselves.

For those who prefer the gag-o-meter turned up to 11 on their election coverage, there's The Vote Now Show. Steve Punt, Hugh Dennis and the rest of the hardworking Now Show team are offering comedic biteback three nights a week for election season, with programmes being recorded just four hours before transmission to make sure they're bang up to date on the day's events.

On Monday, Andy Zaltzman subjected himself to a John Humphrys interview (Humphrys is delightfully game), while Jon Holmes' consideration of stirring theme tunes for party leaders provides the belly-laugh we all sorely need. Tuesday's instalment included John Finnemore's hilarious dos and dont's for campaign leaflets - horse illustrations are key, apparently.

Podcast: John Finnemore interview

In a very special edition of the Rum Doings podcast, we are joined by comedy writer John Finnemore. We have discussed Mr Finnemore's work on Rum Doings in the past, especially the fantastic Radio 4 sitcom Cabin Pressure.

Only on radio, where the listener brings the scenery, can a comedy about a small airline take off so successfully. (I'm a devoted fan of that ultra-camp TV show The High Life, but it only had one series.) This has the setting and characters from which classic sitcoms are built: a struggling business, a canny but inexperienced proprietor (Stephanie Cole), her wily chief pilot (Roger Allam), his ambitious young rival (Benedict Cumberbatch) and the good-hearted but daft son of the boss (John Finnemore, who's also the writer). It's really funny.

Welcome return for John Finnemore's situation comedy about a struggling small charter airline. It's blessed with a classy cast, Roger Allam, Benedict Cumberbatch, Stephanie Cole as Carolyn, the boss, and Finnemore himself as her perennially perky son Arthur. And today Alison Steadman arrives as Carolyn's sister. They haven't spoken for years. Arthur hasn't bothered to think about that as he's planned a cheery birthday trip for them all. To Helsinki. He's booked it on his Mum's credit card. And she thought it was proper business.

For the last six weeks, there has been one reason at least to put away the razor blade - a weekly appointment with Cabin Pressure, one of the funniest sitcoms ever to air on the radio.

It is always a puzzle to me as to why I sit through so much comedy with a 'We are not amused' expression when I find most of what goes on in real life belly-achingly diverting. Similarly, it is almost impossible to analyse the secret of good comic writing but John Finnemore's script for the six-parter had it in spadefuls.

So Finnemore, who has also written for Dead Ringers and Mitchell and Webb, had his characters with incompetence ranging against dry wit, and his landscape, that surreal world in the sky which is an airliner in transit. It could still have all gone wrong but his ear for a comic retort was equal to his instinct for a comical situation. The result was a six-week abdominal workout for listeners and, I hope, a recommission for Pozzitive Productions.

I gave the show a brief mention a few weeks ago, but now its run has finished, it's time to give Cabin Pressure its due. Its first episode was, I said, flawless. Nothing can be flawless for ever, but the writing and performances in this tight comedy have been exceptional. Let me put it like this: this is the only programme that has kept me close to a radio at 11.30 every Wednesday morning. Never mind Listen Again - you want to catch this as soon as you can.

The setting might be novel - a charter plane, with its skeleton crew of misfits - but the writing obeys pretty much all the necessary rules of classic British sitcom writing, which are simple. In fact, students of the art form would do well to listen to it and take notes. You need little more than an inverted class relationship, a sense of failure, an idiot, and a scary authority figure. What writer John Finnemore has done as well is to add, without tilting things off balance comedy-wise, some depth to the characters.

So the dragon of a boss, played by Stephanie Cole, is revealed to be scared of becoming a 'little old lady'; and the wonderfully supercilious Jeeves/Sergeant Wilson figure, the man who should be Captain but isn't (a perfect performance by Roger Allam), is shown to have weaknesses of his own. The show deserves an award.

The fourth edition of this five-star sitcom opens with what is now a running joke on how the budget airline crew either don't know or don't care about the technicalities of taking off, flying or landing.

I've listened every week, expecting it to crash land but John Finnemore's writing flies in first class. And then there's Roger Allam's performance as the bitter first officer who despises his captain. He is to sarcasm and sneering what Rowan Atkinson's Blackadder was to, well, sarcasm and sneering. Radio sitcom success stories are rare: let's hope this one's in from the long haul.

John Finnemore's new situation comedy has the benefit of a superb cast. Roger Allam, Stephanie Cole and Benedict Cumberbatch give their all to this story of a small charter airline whose single plane is flown by one blasé old know-it-all (Allam) and one fiercely competitive young thruster (Cumberbatch). The whole shebang is owned by a fearsome divorcée (Cole) who has come by the plane in a divorce settlement. Her other inheritance is a dim son (played by the author) whose meek optimism is amply reflected in the laughter from the studio audience.

The fear and joys of flying have been a comedy staple for decades, and every joke it is possible to make has probably been made. The challenge is to tell the old jokes in a new way. So step forward, experienced wordsmith (Dead Ringers, That Mitchell and Webb Sound) John Finnemore, with this new six-part sitcom about a one-plane outfit run by an autocratic divorcée (Stephanie Cole, doing her usual posh bully bit).

Her aircraft has two pilots, one a jaded cynic with a dodgy past who can, though, actually fly (played to worldweary perfection by Roger Allam) and one who seemed to have got his wings through a correspondence college (Benedict Cumberbatch, showing he can do situation comedy as well as he does everything else in the thesp game).

Chuck in Finnemore himself as Cole's keen but dim son-of-all work, plus an unusually high level of well-researched technical information about flying, and you have a half-hour that flies by (fnaarg fnaarg).