I never pre-plan a picnic. I've flown with are Jet* and Virgin Blue in Australia but as the flights were only an hour long or so I didn't bother bringing my own food onboard or even buy any snacks. The only other time was on Virgin Express from BRU-FCO which was just under 2 hours long and I bought a sandwich only because the price was reasonable and I didn't have anything to eat on a previous 2.5hr journey.
Even with flights under 3 hours I don't need any food. I just make sure I'm well fed before I fly and bring my own drinks and maybe a chocolate to munch on.