Aircraft is probably referring to capacitor bank. They look like a six-pack of beverage cans.
What gas, amperage, tungsten type and diameter are you using. Argon starts easier than helium or argon/helium or helium/argon gases. Tungsten is a poor conductor of electricity and it needs to be "hot" to be a good starter. Use the smallest tungsten for the amperage you are welding. In other words, don't use a 1/8" tungsten to weld 1/16" material thickness at say 50-75 amps. Don't use thorium alloyed tungsten for ac. Use pure, zirconium or cerium.
Hope this helps.