Learn English – Words associated with throwing things, specifically the action of throwing a paper airplane

I think originator may convey the meaning:

• someone who creates new things

Also a conceiver or a mastermind according to context.

Source: www.thefreedictionary.com

You could coin a couple on the model of defenestrate (a verbal back-formation from defenestration).

Coinages Based on Modern French

Maybe abvoiturate, although it doesn't convey the 'moving' concept, so

a traveling abvoituration.

Then for rooftop, a tougher nut to crack, perhaps

detoitate.

Note and disclaimer on the French-based coinages: I don't speak or read French, so the choice of terms for the base coins may be inappropriate, although I selected those to the best of my ability by analyzing a variety of possibilities. My confidence in 'detoitate' is high for the simple reason that I only found one translation from English 'rooftop' to French: toit. My confidence in 'abvoiturate' (and so 'abvoituration') is only slightly compromised by my having found these possible translations of 'car' into French: autocar, car, tram, voiture, wagon. Of those, however, only voiture covered a satisfying range of meanings when translated back into English. Those meanings included "car", "carriage", "coach", "motorcar", and "vehicle".

However, as a comment on the initial version of this answer brought to light, using French words for the base coin was premised on my misreading of the etymology of 'defenestration'. For this reason, the French-based coinages are not (as I may appear to claim) strictly on the model of 'defenestrate', which derives from Latin fenestra, meaning "window".

French-based coinages are workable, but the heyday of French adoptions in English is long past. Much more common today are coinages based on Latin or ancient Greek whenever a word is wanted in English and not ready to hand from another modern language.

Coinages Based on Latin

For an ejection from a vehicle, the verb,

abvehiculate

could be used. The substantive form would be (for a moving vehicle),

a traveling abvehiculation.

For tossing off a rooftop, a slight correction of an offering from a comment on the initial version of this answer may be good:

detectate.

Note on the Latin Coinages: My confidence in these coinages is fairly high. I did complete post-graduate study of Latin, enough to read and write the language with what was considered 'proficiency' at the time, although admittedly 30-some years have intervened between those studies and today. During those intervening years such proficiency as I attained has diminished, rather than increased.

The first, 'abvehiculate' (and so 'abvehiculation') derives from vehiculum, meaning "a vehicle, conveyance". This word may be applied generally, that is, not only to automobiles, but to any type of vehicle, including watercraft.

The second, 'detectate', derives from tectum, meaning "roof". Tectum, in turn, is a substantive formed from the past participle of tego, meaning "to cover, conceal". Hence also the existing English word 'detect', meaning "to uncover, reveal".

Note about the prefixes and suffixes:

The prefix 'ab-' is used in the sense of "off, away, from". The prefix 'de-' is used in the sense of "down from".

The use of the suffix '-ate' is complicated. A brief excerpt from the OED may suffice to explain the formative use:

... it became the recognized method of englishing a Latin verb, to take the ppl. stem of the Latin as the present stem of the English; so that English verbs were now formed on Latin pa. pples. by mere analogy, and without the intervention of a participial adjective.

["-ate, suffix3". OED Online. September 2015. Oxford University Press. http://www.oed.com/view/Entry/12404?rskey=MBq95g&result=5&isAdvanced=false (accessed October 31, 2015).]

The excerpt, of course, considerably oversimplifies a long, convoluted story about the use of '-ate' to english Latin and French words.