There are 15 11-letter words that start with 'plan'.
| planarities | planchettes | planenesses |
| planetaries | planetarium | planetoidal |
| planetology | plangencies | planimeters |
| planimetric | planisphere | planography |
| plantations | plantigrade | plantocracy |
Note: These 15 11-letter words that start with 'plan' are found from the USA & Canada version of the tournament Scrabble word list.
Also see words start with plane, plant, plani, plana, plank, planc, plann, plano, planu, plang, planl, planf, plans.
5-letter words start with 'plan' (4)