Ray(s) to plane (flat) intersection?

I want some fast code to calculate the 3D point of intersection of a ray against a plane (which is actually flat - stretching out in the X and Z planes only - so might be faster).

Also, I'm wondering if there is any way to speed this up for multiple parallel rays against the same plane (ignoring that I only need to calculate the plane equation once). Anyone got any pointers?

'AB is a line, not a ray
'flags
'1 - two-sided
'2 - infinite ray
Function LineIntersectsPlane:Int(Ax#,Ay#,Az#,Bx#,By#,Bz#,nx#,ny#,nz#,d#,flags=0,epsilon#=0.0)
Local vec:TVec3
Local u#
If Not (1 & flags)
If PointPlaneDistance#(Ax#,Ay#,Az#,nx#,ny#,nz#,d#)>=-epsilon Return 0
EndIf
u#=(-nx*Ax-ny*Ay-nz*Az+d)/(-nx*(Ax-Bx)-ny*(Ay-By)-nz*(Az-Bz))
If (u>=epsilon And u<=1.0+epsilon)=True Or (2 & flags)<>0
VECTOR_x=Ax+(Bx-Ax)*u
VECTOR_y=Ay+(By-Ay)*u
VECTOR_z=Az+(Bz-Az)*u
Return 1
EndIf
Return 0
EndFunction