I travel by airline a lot, typically 35 weeks a year, sometimes overnight, sometimes all week or more. Always travel with a checked bag as I need my knives. Threw this list together from memory, probably left a few items off.

Except as noted, this is what I carry on in my Rollerboard and Rolling Computer Case and on my person
* = Checked Baggage
# = Carry-on and Checked baggage

Tools and such:

Verizon Droid Razr MAX Smart Phone (will last 2 days standby regular, 3 days when set to economy)
ToughBook computer (7 hrs battery life)
6 ft. extension cord w/ 3 receptacle, three way plug, and Charge Cables for devices
Sidewinder Charger for cell phone *
TSA Compliant Leatherman Knifeless Fuse
3.5" Scissors
Assortment of flashlights (varies, but typically about 4-6 ranging from PICO/Photon to 100+ lumen)
Spare batteries for flashlights #
Various Multi-use pens :-)
BIC Lighter, vacuum packed
Book Matches, vacuum packed *
RSK Mk1 and Mini-RSK Mk1 Knives *
Leatherman Charge *
Leatherman Juice S2 *

(I carry 2 sets knives and tools for both less formal and business dress)

Supplies:

4 x 26" rolls duct tape
48" roll fluorescent pink gaffer tape
48" roll 3/4" fiberglass reinforced strapping tape
AMK PSP (with scalpel blade removed)
2 x X-Large Binder Clips (keep drapes closed) *
Howard Leight MAX Earplugs (lots) #
50 ft. Parachute Cord *

Food & Water:

Water (purchased at airport and local upon arrival)
Various LaraBars and "Granola" Bars #
3 x Starkist Lemon Pepper Tuna (retort packaged) & Primus Folding Spoon/Fork (NOT a spork!) #
Jerky or similar

Environmental Protection:

Emergency Poncho
Compact Umbrella
6 x Sperian Fold Flat N95 Masks w/ Exhalation Valve #
6 pair Nitrile gloves (vacuum packed)#
1pr. Nylon Work Gloves with Coated Palms/Fingers, vacuum packed *
30 x Chlorine Dioxide water purification tablets

First Aid:

LOTS! #
Assortment of OTC and prescription meds to cover typical on-the-road maladies
Personal Meds (adequate for 1 week beyond planned trip length) w/ copies of current prescriptions

Misc:

Emergency Cash, Spare Credit Card, Prepaid Phone Card (well hidden)
Spare Drivers License (just report lost/stolen and get a replacement, keep old one - AZ are good for damn near forever, YMMV)
ACR ResQLink PLB
Lightweight Backpack (folds into its own pocket), vacuum packed