1,000 for IFR-IFR. 500 for IFR-VFR. This can be reduced provided there is
visual contact and the visual separation is maintained by the pilot.


From Faa Order 7110.65 (ATC)

Section 5. Altitude Assignment and Verification

4-5-1. VERTICAL SEPARATION MINIMA

Separate instrument flight rules (IFR) aircraft using the following minima
between altitudes:

a. Up to and including FL 290- 1,000 feet.


7-7-3. SEPARATION

Separate VFR aircraft from VFR/IFR aircraft by any one of the following:

a. Visual separation, as specified in para 7-2-1, Visual Separation, para
7-4-2, Vectors for Visual Approach, and para 7-6-7, Sequencing.

NOTE-
Issue wake turbulence cautionary advisories in accordance with para 2-1-20,
Wake Turbulence Cautionary Advisories.

b. 500 feet vertical separation.

c. Target resolution when using broadband radar systems. The application of
target resolutions at locations not using broadband radar will be
individually approved by the Program Director for Air Traffic Planning and
Procedures, ATP-1.





wrote in message
...
Is 1000 feet the absolute minimum vertical separation between ifr
aircraft? Or can atc assign 3500 feet to one, and 4000 to another,
and have no lateral separation??

Secondly, any different for a situation where one is ifr at 4000 ft,
and a vfr aircraft is being vectored at 3500 feet, with no lateral
separation?

Any exceptions?

Stan