I'll second Robin's suggestion. In the past I have weighed my (cheap) rucksack cover in a padded envelope and applied the correct postage stamps in advance. That way all you have to do is pop it into the nearest post box rather than look for a post office.

I have a Highlander pack cover which I use when flying with my pack. I keep my compass, maps and other personal stuff to carry on in one of those very light weight foldable bags. My walking sticks collapse down and attach to pack inside the cover. Never had a problem!

I flew to Inverness last year.

I had an old roll top stuff sack/bag liner in my cupboard that was big enough to put the rucksack in.

It only weighed about 80g so I just used it as a rucksack liner for the challenge (I always store everything in individual sea to summit sil-nylon roll top bags so this was an additional layer).
It might have been useful if we'd had a downpour, but it wasn't in the way on a sunny crossing.

I was glad I carried it with me because I had to abort my crossing in Newtonmore and return home because of a family illness, it was easy (but not cheap) to rearrange my flight.

I used one of my small roll-top bags to keep all my electronics and papers in as hand-luggage which worked well for no extra weight.

Cheers guys, i think i'll try the osprey bag thingy and use it as my pack liner maybe

I’m not sure that the Osprey packcovers are 100% watertight to use as a packliner. You might want to get a Tread Lite Gear polythene packliner to be totally safe.

https://www.treadlitegear.co.uk/tread-lite-gear-72l-polypaq-jumbo-clear-rucksack-dry-bag-liner-ultralight-52g-205-p.asp

Quite robust and only weigh 52g. I use them all thetime now. Much cheaper than cuben fibre!

Is it up to two weeks in the highlands? just looks like a placcy bag

The Tread Lite plastic bag is decently robust as a packliner. I wasn’t suggesting it as a rucksack cover for air travel. My Osprey Transporter (previous version) is waterproof but the seams aren’t sealed so is vulnerable if you want to use it as a waterproof pack liner. Hence I was suggesting using a Tread Lite liner which only weighs 52g.

Slightly heavier option than suggested here.160g ish
I used one of these for a Ryanair flight this year and used it for a groundsheet in my porch.
https://www.ebay.co.uk/itm/192663741106

Alternatively and cheap I know people swear by these laundry bags

https://www.ebay.co.uk/i/112526960659?chn=ps&var=412913767026

Cheers guys i'll take a look at all three links

appreciate the help :+1:

I've flown with my backpack from the USA to the Uk and Europe more times than I can remember and have, in the last 10 years, used one of those zippered IKEA bags used to store duvets and the like. They're £3 and I have sent them on to Montrose for the return if necessary. I even shove my poles and boots in these bags along with the pack. It's not like I can go anywhere if I'm wearing the boots and the oack doesn't arrive anyway. Yes, they're see-through and I just bungee around it or tie a string. I carry a plastic carrier bag with camera, compass, important/small expensive items. Never had a problem.

This bag, any bag, will get scuffed up during baggage handling. This is not the time to go lightweight. When backpacks were made with thicker, more robust materials you could get away with securing the waist belt backwards around the base of the pack and let them take it that way.

Good luck!