If you fly an RC plane that isn't electric powered then you need to give thought to the type of battery technology you use to power the RC gear.
The old AA size Nicad or NiMH packs simply are not suitable for many of today's larger glow/nitro, gas or turbine-powered RC planes because they can't reliably deliver enough current to support the demands of hi-torque or hi-speed digital servos.
Lithium battery technology has made the older Nicad/NiMH batteries all but redundant because it offers a cheaper, more reliable, higher current option without the problems of "memory" or high self-discharge.
These days I'm increasingly using LiFe packs for my receivers/servos and have yet to experience a failure. A123 packs are also based on LiFe chemistry but have "nanotech" construction which effectively gives them a higher 'C' rating so they can deliver more current.
Given that LiFe a 1100mAH pack costs under $4, a 2000mAH pack can be bought for under $15 and a 4200mAH pack for around $30 -- it makes no sense to rely on older technology batteries that may not be up to the task in your larger non-electric RC planes.