I usually do it on own with my two every year - July this year and through Korea for the first time (cheap flights!). I've had some really good flights with ds1 from age 3 (he's now 8) but absolute flights from hell with ds2 who is energetic at the best of times. Last flight home with him was like a black comedy resulting in woman in seat behind having a breakdown about 8 hours into flight and screaming for gods sake shut him up!!!!!!!! Very helpful, if I'd had phenergan I would have taken it myself . In fact most of my stories tend not to be too positive - ds2 last time threw plate of food behind him into lap of person behind, his bottle on sleeping woman's head, litre bottle of water on my seat before take off, food down my t-shirt etc etc...I have to add I was tending to ds1 each time and not swigging free wine or having a snooze! Anyway alot depends on the child.
I havn't used phenergan. They say try it 3 times before you fly as it has the reverse effect in some children (eg my step son who was wired for 24 hours). They say they might not react the first time which is why they say give it three goes!?!?!?
We always do at least a 12 hour stop and check into hotel, shower let them run around, swim in hotel pool, feed them non airline food etc...I actually think it's more for me than them, it's a mini sanity break.
Unless you really need them don't bother with car seats on flights, nobody will help you cart them and your bags through passports and when changing planes. Trying to run after a toddler with car seat, cabin size backpack and carry on bag is not fun.
Ask for them to keep your food while you feed children, then get them to clear theirs while you eat yours so you don't end up wearing more than everybody eats.
Be militant about the basinette and pre-book if you can. With a 6 month old you should be OK, they tend to favour younger children if there are too many. Do strap them in, even at 4 months they do fall out (didn't want to wake him). Lesson learnt there.
Rest usuals - wrap little $2 shop presents that are exciting to open but don't matter if they fall on the floor and get lost. Colourings, books, favourite teddy to use as a pillow.
Make a big deal about being on your own to cabin crew they sometimes can have you escorted to front of all queues (passport etc) which is a god send - trying to not lose a toddler under the ropes in a queue, watch your bags and other child can be rather challenging.
If all else fails cry hysterically - somebody usually helps then and chant the mantra - it's only 26 hours....
Roll on fast planes I say....