Angular Momentum of an airplane

[lunarskull]

An airplane of mass 12000kg flies level to the ground at an altitude of 10. km with a constant speed of 175 m/s relative to the earth. (a) what is the magnitude of the airplane's angular momentum relative to a ground observer directly below the airplane? (b) Does this value change as the airplane continues its motion along a straight line?

desperate...was out with the flu now I am lost
so L= r X Mv...
L=r??X (12000)(175)
r=10??
so 10X(12000)(175)
21000000. this doesn't look correct...

 

[Hootenanny]

What equations do you know that relate linear velocity with angluar momentum (assuming the Earth is spherical)

 

[lunarskull]

What equations do you know that relate linear velocity with angluar momentum (assuming the Earth is spherical)

just edited first post. i guess maybe
I=(2/5)Mr^2 might come in handy?

 

[Hootenanny]

$L = Mvr$ would be easier to use with regards to the plane, where $r$ is the radius of orbit and v is linear velocity.