I generally watch the tv's when they have them fitted but chances are I'll have ipad with me too. Long haul I'll definitely have noise cancelling headphones too. Seldom travel without them.
I wouldn't take a laptop just to watch movies on a plane but if it was going anyway (I'd probably take mine for photo editing) then I could use it
Packard Bell ZG5 (basically an Acer Aspire 150) with a 240GB SSD (OCZ Agility 3) and an aftermarket 14400mAh 12-cell battery. This allows for around 12 hours of constant movie viewing, which is enough for intercontinental travel (something I do way more often than I'd like).
Performance on Mint MATE 17.2 is okay, but nothing to write home about. Weirdly enough, it's wicked fast and runs longer on a single charge when running ... Vista. Yeah, go figure.
As for audio, a set of Bose QC20 noise-cancelling headphones. Best noise cancellation you can get.
My normal laptop with the insane CPU throttled to hell (i7-4700MQ@30% or less). And the 1TB (soon to be 2TB?) internal HDD and a 120GB SSD as boot..
I avoid having external HDDs when I travel anywhere. Really wish WD would get into the 9.5mm thing for 2.5" drives. Would be nice... currently it is just Samsung/Seagate. The other route is a 2TB SSD, an insane expense though.
My last flight was a nice read through a book on my nook. No crying children that time though, so lucky me.
13" MacBook Air. Ya I know it's a Mac but it's light, snappy and can play some old games with ease. Plus the battery life on it is great for those cross country trips I do every year.
Ebay. I bought the netbook in the summer of 2008. By late 2011 the original 2200mAh 3-cell only lasted for about an hour anymore (from 3 hours when it was new), so I decided to look for a slightly larger one. I found this one for about 45 EUR and I just couldn't resist.
I usually don't trust those Chinese aftermarket batteries due to all the horror stories you read everywhere, but I took a gamble and it paid off. After nearly 4 years, hwmonitor indicates that it is only 10% worn.
Also note the remaining battery life. Last week I read about the 2015 Macbook's "all day battery life" of up to 9 hours. It's soooo hard not to laugh when you read that.