<s>
An	O
airport	O
with	O
a	O
mandatory	B-Algorithm
frequency	I-Algorithm
(	O
MF	O
)	O
,	O
mandatory	B-Algorithm
traffic	I-Algorithm
advisory	I-Algorithm
frequency	I-Algorithm
(	O
MTAF	B-Algorithm
)	O
or	O
air/ground	O
radio	O
(	O
A/G	O
)	O
is	O
an	O
airport	O
which	O
does	O
not	O
have	O
a	O
control	O
tower	O
but	O
still	O
requires	O
arriving	O
and	O
departing	O
aircraft	O
to	O
communicate	O
with	O
other	O
aircraft	O
or	O
a	O
radio	O
operator	O
on	O
a	O
published	O
frequency	O
.	O
</s>
<s>
Mandatory	B-Algorithm
frequency	I-Algorithm
airports	I-Algorithm
are	O
rare	O
in	O
the	O
United	O
States	O
,	O
one	O
example	O
being	O
Ketchikan	O
International	O
Airport	O
(	O
)	O
,	O
but	O
they	O
are	O
common	O
in	O
other	O
countries	O
such	O
as	O
Canada	O
,	O
Australia	O
,	O
the	O
United	O
Kingdom	O
and	O
Norway	O
;	O
often	O
,	O
an	O
MF	O
or	O
MTAF	B-Algorithm
airport	O
is	O
one	O
with	O
scheduled	O
passenger	O
service	O
but	O
insufficient	O
traffic	O
to	O
support	O
a	O
control	O
tower	O
.	O
</s>
<s>
If	O
there	O
is	O
a	O
flight	O
service	O
specialist	O
monitoring	O
the	O
frequency	O
,	O
the	O
specialist	O
will	O
give	O
pilots	O
advisories	O
about	O
traffic	O
,	O
weather	O
,	O
and	O
surface	O
conditions	O
,	O
and	O
may	O
relay	O
IFR	O
clearances	O
from	O
en	O
route	O
controllers	B-Application
,	O
but	O
cannot	O
give	O
clearances	O
themselves	O
.	O
</s>
