Acknowledgement and permision to enter airspace, depends on the airspace.

For Delta airspace, all you need is for the tower to have responded to you by your N-number.. Even if it's just to say "stand-by".. The fact that they say your number, is an OK to enter.

For Charlie airspace it's about the same. More times than not, their first response will be a vector.. You need some sort of "direction" from them.. not just an acknowledgement (and they know that.. so 99 times out of 100, they'll either give you a vector to enter.. or a vector to remain clear until they can fit you in.

For Bravo airspace... you need to hear the EXACT phrase, "Cleared to enter the Bravo airspace".  It doesn't even matter if they give you a vector to expect... if the transmission does not include, "Cleared to enter the Bravo airspace", you must remain clear..

(this is from memory and how we do things around here.. but it's probably accurate)

MSFS ATC is a little "off", but it's about as accurate as you can get, without devoting an entire software title to it (and probably a seperate computer). What is "kinda" realistic about it is.. that you won't be handed off to a tower during either FF or an IFR flight. Just like for real; your only communications with towers, will be while taking off.. or asking to land. Once you take off, you'll be talking to a succesion of Controls(sub-divisions of major Centers) and Approaches (as you pass near larger airports)... Your very first contact after taking off is called "Departure", but it's the same thing as "Approach" .. sometimes sharing the same frequency. At larger airports there are more than one "Approach/Departure", depending on from which direction you're departing or approaching.

We shuttle planes from KOSU (Delta airspace) over to KCMH (Port Columbus International Charlie airspace) and back for maintenance all the time... It takes SEVEN seperate conversations to get in/out of Charlie airspace... add FOUR for Delta airspace.. and one ATIS per airport, and wev'e got 13 radio operations  ..


Here's a mock trancript of the short, round-trip (KOSU airspace is actually under the top shelf of KCMH airspace)....

You:  Ohio State Ground, Cessna 4790G, East ramp, 090 with Tango
ATC: 90G, State Tower, taxi to 27L via Alpha Delta
You:  State Tower, 90G ready at 27L
ATC: 90G, State Tower, cleared for takeoff, 27L, runway heading to the river, then on course
You:  Cleared on course after the river, 90G
***** when clear of the pattern and on course and after listening to KCMH ATIS****
You: State Tower, 90G for a frequency change (if still in Delta airspace, else skip these two steps)
ATC:  90G, State Tower, frequency change approved
You:  Columbus Approach, Cessna 4790G, just off OSU at 2000, inbound, full-stop going to Lane Aviation
ATC:  November 90G, Columbus Approach,altimeter 2992, maintain 2000, fly heading 120, squawk 2345, expect runway 28R
You:   2000, 120, 2345, 28R, 90G
ATC:  November 90G, Columbus Approach, contact tower on 132.7
You:   132.7, 90G
You:   Columbus Tower, 4790G at 2000, inbound
ATC:  November 90G, make an abbreviated base at the 28R numbers now, and I can get you in in front of the 757 on 7 mile final.
You:   At the numbers now, 28R, 90G
ATC:  90G, Cleared to land, 28R
You:   28R, 90G
ATC: November 90G, exit next taxiway, contact ground on point niner (all grounds are 121.X)
You:  Point niner, 90G
You:  Columbus Ground, 4790G, clear of 28R on Foxtrot
ATC: 90G, Taxi to Lane
You:  90G

***take care of business*****

You:   Clearance Delivery, 4790G at Lane, VFR to OSU with Hotel
ATC:  November 90G, Clearance Delivery, squawk 5432, taxi to runway 28R via Charlie, Charlie one, contact tower when ready
You:  28R, 90G
You:  Columbus Tower, 4790G, ready at 28R
ATC: November 90G, runway heading, cleared for takeoff runway 28R
You:  Runway heading, 90G
ATC:  November 90G, contact Columbus Departure on 119.25
You:   19 25, 90G
You:   Columbus Departure, 4790G, direct OSU, airport in sight.
ATC: November 90G, Columbus Departure,  frequency change approved

*****listen to KOSU ATIS*******

You:   Ohio State Tower, 4790G off CMH at 2000, inbound, full-stop with Uniform
ATC:  90G, State Tower, fly straight in, runway 27L, report 2 mile final
You:   two miles, 27L, 90G
You:   State Tower, 90G at two miles
ATC:  90G, State Tower, cleared to land, 27L
You:   27L, 90G
ATC: 90G, State Tower, left at Delta, monitor point seven to park...
You:  90G...


ALL  of  THAT... just to fly two, 5 mile legs..